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.     

Site of stimulation by mannosyl-P-dolichol of GlcNAc-lipid formation by microsomes of embryonic chick retina

Mannosyl-P-dolichol (man-P-dol) has been shown to stimulate the early reactions of the dolichol pathway, specifically, the biosynthesis of GlcNAc-P-P-dol and GlcNAc-GlcNAc-P-P-dol, and thus may play a regulatory role in glycoprotein biosynthesis. The site of action of man-P-dol has previously been suggested to be the GlcNAc-transferase concerned with the formation of the monoglucosaminyl derivative. Since the concentration of the chitobiosyl compound also increases as a result of the presence of man-P-dol, the immediate site of the activation was reexamined. The effect of man-P-dol on the formation of GlcNAc-GlcNAc-P-P-dol using GlcNAc-P-P-dol synthesizedin situ or added exogenously as the substrate was investigated. In addition, the distribution of radioactivity in the glucosaminyl constituents of the products under the stimulatory conditions was determined. The results of these studies supported the conclusion that the stimulation of GlcNAc-lipid synthesis by man-P-dol is due to the enhanced synthesis of GlcNAc-P-P-dol. It is not a result of the activation of the GlcNAc-transferase catalyzing the attachment of the second GlcNAc residue for the biosynthesis of the chitobiosyl derivative.Abbreviations GlcNAc-P-P-dol N-acetylglucosaminylpyrophosphoryldolichol - GlcNAc-GlcNAc-P-P-dol N-acetylglucosaminyl-N-acetylglucosaminylpyrophosphoryldolichol; - chito N-N-diacetylchitobiose - man-P-dol mannosylphosphoryldolichol - TX-100 triton X-100 - Tes 2-{[tris-(hydroxymethyl)-methyl]-amino}-ethanesulfonic acid     

Sequences within the poliovirus internal ribosome entry segment control viral RNA synthesis.

The 5' untranslated region of poliovirus RNA has been reported to possess two functional elements: (i) the 5' proximal 88 nucleotides form a cloverleaf structure implicated in positive-strand RNA synthesis during viral replication, and (ii) nucleotides 134 to at least 556 function as a highly structured internal ribosome entry segment (IRES) during cap-independent, internal initiation of translation. We show here that the IRES itself is bifunctional and contains sequences necessary for viral RNA synthesis per se. For this purpose, we used a dicistronic poliovirus RNA in which the translation of the viral non-structural (replication) proteins is uncoupled from the poliovirus IRES. In this system, RNA synthesis is readily detectable in transfected cells, even when the poliovirus IRES is inactivated by point mutation. However, deletion of the major part of the poliovirus IRES renders viral-specific RNA synthesis undetectable. Using the same system, we show that a three nucleotide deletion at position 500 in the 5' untranslated region drastically affects both translation efficiency and RNA synthesis. Furthermore, disruption of the secondary structure of the IRES around nucleotide 343 has minimal effects on IRES function, but dramatically reduces viral RNA replication. Taken together, these results provide direct evidence that sequences essential for viral RNA synthesis are located in the 3' region of the poliovirus IRES.     

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.     

The time-course of energy balance in an isometric tetanus

Unpoisoned sartorius muscles of Rana temporaria were stimulated tetanically in isometric contractions lasting up to 20 s at 0 degrees C. The observed enthalpy (heat + work) production and the chemical changes in these contractions were measured, and a comparison was made between the observed enthalpy and the enthalpy that could be explained by the chemical changes. Like earlier workers, we found that the only net known reaction of energetic significance that occurred was dephosphorylation of n-phosphoryl creatine (PC), and we found a significant evolution of unexplained enthalpy (UE), a portion of the observed enthalpy which could not be explained by the extent of PC dephosphorylation. We measured the total quantity and the rate of production of the UE, and we found that its rate of evolution, which was most rapid during the first 750 ms of contraction, fell progressively to zero by the 8th s of contraction: i.e., after 8 s of contraction, all the observed enthalpy is adequately explained by PC dephosphorylation. The time-course of evolution of the UE was slower than that of the labile enthalpy (a component of the enthalpy evolved in isometric contraction whose rate of production declines exponentially at approximately 1 s-1). We conclude that, although the magnitudes of these enthalpy quantities may be similar, they are not derived from the same chemical reaction in muscle.     

Metal-ligand vibrations of cyanoferric myeloperoxidase and cyanoferric horseradish peroxidase: evidence for a constrained heme pocket in myeloperoxidase

The low-frequency FeCN vibrations of cyanoferric myeloperoxidase (MPO) and horseradish peroxidase (HRP) have been measured by resonance Raman spectroscopy. The ordering of the frequencies of the predominantly FeC stretching and FeCN bending normal vibrational modes in the two peroxidases differs. These normal mode vibrations are identified by their wavenumber shifts upon isotopic substitution of the cyanide ligand. For MPO, the stretching mode nu 1 (361 cm-1) occurs at a lower frequency than the bending mode delta 2 (454 cm-1). For HRP, the order is reversed as nu 1 (456 cm-1) is at a higher frequency than delta 2 (404 cm-1). Normal coordinate analyses and model complexes have been used to address the origin of this behavior. The nu 1 stretching frequencies in cyanide complexes of iron porphyrin and iron chlorin model compounds are similar to one another and to that of HRP. Thus, the inverted order and altered frequencies of the nu 1 and delta 2 vibrations in MPO, relative to those in HRP and the model compounds, are not inherent to the proposed iron chlorin prosthetic group in MPO but, rather, are attributed to distinct distal environmental effects in the MPO active site. The normal coordinate analyses for MPO and HRP showed that the nu 1 and delta 2 vibrational frequencies are not pure; the potential energy distributions for these modes respond not only to the geometry but also to the force constants of the nu(FeC) and delta(FeCN) internal coordinates.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Selective inhibition of acyl-CoA dehydrogenases by a metabolite of hypoglycin.

Extracts of liver mitochondria from donor rats given hypoglycin, the toxic amino acid from the ackee plant (Blighia sapida) showed drastically reduced levels of acyl-CoA dehydrogenase activity with butyryl-CoA as substrate. Activity with octanoyl- and palmitoyl-CoA was unaffected. Evidence that the active agent is methylenecyclopropylacetyl-CoA, a hypoglycin metabolite, was obtained by observing effects of the compound on a partially purified enzyme mixture prepared from rabbit liver. At 13 muM concentration, it strongly inhibited butyryl-CoA dehydrogenase (EC 1.3.99.2) with butyryl-CoA as substrate; it was far less effective with palmitoyl-CoA as substrate for the other similar enzymes present in the preparation. Unlike normal substrates of the acyl-CoA dehydrogenases, the compound itself, and not a reaction product, is inhibitory. The observed effect is consistent with quite general inhibition of fatty acid beta-oxidation by hypoglycin.     

Isolation of a branched-chain alpha-keto acid decarboxylase from rat liver.

An enzyme which catalyses oxidative decarboxylation of branched-chain alpha-keto acids was extracted from rat liver mitochondria with the aid of NaClO4. Purification yielded a product which appeared homogenous upon electrophoresis. Some kinetic data are reported; however, the enzyme is inactive with alpha-ketoisovalerate. The tenacity of binding to mitochondria, specificity, and other features, suggest that the decarboxylase may be a component of an enzyme complex named alpha-ketoisocaproate: alpha-keto-beta-methylvalerate dehydrogenase.