Pharmacology of DMSO

A wide range of primary pharmacological actions of dimethyl sulfoxide (DMSO) has been documented in laboratory studies: membrane penetration, membrane transport, effects on connective tissue, anti-inflammation, nerve blockade (analgesia), bacteriostasis, diuresis, enhancement or reduction of the effectiveness of other drugs, cholinesterase inhibition, nonspecific enhancement of resistance to infection, vasodilation, muscle relaxation, antagonism to platelet aggregation, and influence on serum cholesterol in experimental hypercholesterolemia. This substance induces differentiation and function of leukemic and other malignant cells. DMSO also has prophylactic radioprotective properties and cryoprotective actions. It protects against ischemic injury.     

Cat satellite DNA. Isolation using netropsin with CsCl gradients

The absence of centromeric bands in the karyotype of Felis catus is confirmed. It is also confirmed that no satellite band is visible in CsCl density gradients. However, a satellite is observed both by recentrifuging the fraction of the DNA that bands at high density in CsCl and by using netropsin to enhance the resolution of a CsCl gradient containing total F. catus DNA. The satellite, about 0.5% of total DNA, was isolated by repeated centrifugation in CsCl alone and in CsCl with netropsin. Netropsin was removed and a pure satellite DNA obtained. The reassociation kinetics (C0t1/2 less than 10(-3) M . s) show that the satellite is of the simple sequence type and hence a candidate for centromeric heterochromatin. Its cytological localisation awaits in situ hybridisation experiments.     

Structure—activity relationships in the mutagenicity of quinone methides of 7-hydroxyflavylium salts for Salmonella typhimurium

Several synthetic 7-hydroxyflavylium salts related to apigeninidin, a natural 3-deoxyanthocyanidin, have been studied in the Ames mutagenicity test using strain TA1537 of Salmonella typhimurium. Under the neutral pH conditions of the test, these flavylium salts are deprotonated through ionization of the C7-OH (pK_a′ = 4.2–4.4) to form quinone methides. Only the quinone methides of 4-methyl-7-hydroxyflavylium chloride and 4′-methoxy-4-methyl-7-hydroxy-flavylium chloride showed mutagenicity. Responses of 4–8 times the background were observed at the higher doses (1000 μg/plate), both with and without metabolic activation. It was concluded that the induction of frameshift mutagenicity by this group of compounds is caused by those quinone methides that have non-ionic, stable polycyclic structures at neutral pH.     

Hepatic reactions in erythropoietic protoporphyria (author's transl)

The main hepatic change in erythropoietic protoporphyria is the deposition of protoporphyrin. Brown deposits of this pigment occur in bile canaliculi and ductules, discretely in hepatocytes, and secondarily in macrophages and Kupffer cells. The pigment is deposited in a crystalline form. Under the fluorescence microscope with a mercury maximum pressure burner (HO 50) at a wave length of 380--500 nm, it shows a typical red fluorescence even after paraffin embedding. Its crystalline structure results in a characteristic double refraction under the polarising microscope. Light-microscopically, hepatocellular reactions are characterised mainly by discrete alterations in the ergastoplasm. However, cell damage is indicated by diffusely distributed, hyaline single cell necrosis and by cytolytic piecemeal necrosis at the peripheries of hepatic lobules. Numerous, often disturbed mitoses produce binuclear and multinuclear hepatocytes. The obligatory secretion of protoporphyrin into the bile ducts leads to an alteration in the canalicular and ductular excretion apparatus which involves distinct ductular proliferation and accompanying fibrosis. Piecemeal necrosis is a further consequence of this process. The resulting histological picture is similar to sclerosing cholangitis with which it also has in common the slowly progressive development of hepatic cirrhosis.     

A high‐throughput method to quantify feeding rates in aquatic organisms: A case study with Daphnia

1. Food ingestion is one of the most basic features of all organisms. However, obtaining precise—and high‐throughput—estimates of feeding rates remains challenging, particularly for small, aquatic herbivores such as zooplankton, snails, and tadpoles. These animals typically consume low volumes of food that are time‐consuming to accurately measure.
2. We extend a standard high‐throughput fluorometry technique, which uses a microplate reader and 96‐well plates, as a practical tool for studies in ecology, evolution, and disease biology. We outline technical and methodological details to optimize quantification of individual feeding rates, improve accuracy, and minimize sampling error.
3. This high‐throughput assay offers several advantages over previous methods, including i) substantially reduced time allotments per sample to facilitate larger, more efficient experiments; ii) technical replicates; and iii) conversion of in vivo measurements to units (mL^‐1 hr^‐1 ind^‐1) which enables broad‐scale comparisons across an array of taxa and studies.
4. To evaluate the accuracy and feasibility of our approach, we use the zooplankton, Daphnia dentifera, as a case study. Our results indicate that this procedure accurately quantifies feeding rates and highlights differences among seven genotypes.
5. The method detailed here has broad applicability to a diverse array of aquatic taxa, their resources, environmental contaminants (e.g., plastics), and infectious agents. We discuss simple extensions to quantify epidemiologically relevant traits, such as pathogen exposure and transmission rates, for infectious agents with oral or trophic transmission.

     

β-Xylosidases from filamentous fungi: an overview

β-Xylosidases are hydrolytic enzymes which play an important role in xylan degradation, hydrolyzing xylobiose and xylooligosaccharides to xylose from the non-reducing end. Filamentous fungi are particularly interesting producers of this enzyme from an industrial point of view, due to the fact that they secrete β-xylosidases into the medium. Besides, fungal β-xylosidases are highly advantageous for their elevated activity levels and specificity. Interest in xylanolytic enzymes has been increasing, for their possible application in many biotechnological processes. This fact has driven the isolation, purification and characterization of several β-xylosidases. In this review, the mechanisms of action, substrate specificities, physicochemical characteristics, regulation at molecular level, molecular cloning and classification of filamentous fungal β-xylosidases are described. The potential industrial applications of fungal β-xylosidases will also be presented.     

Indirect assays for deoxyhypusine hydroxylase using dual-label ratio changes and oxidative release of radioactivity

Two procedures for rapid assay of deoxyhypusine hydroxylase activity are described. One of these assays measures changes in the 3H:14C ratio of dual-labeled protein that results from the release of tritium from a specific position in the side chain of the 3H,14C-labeled constituent amino acid deoxyhypusine upon its conversion to [3H,14C]hypusine. The other assay relies upon release of radioactivity from product protein by periodate oxidation of the radiolabeled side chain of component hypusine. The good correspondence of each of these assays with the ion exchange chromatographic method which measures hypusine and deoxyhypusine in acid hydrolysates of protein indicates that each provides a valid means of determining deoxyhypusine hydroxylase activity.     

Effects of EEG of the osmotic opening of the blood-brain barrier in rats

EEG activity was recorded in rats submitted to osmotic opening of the BBB by intracarotid mannitol infusion.This procedure produced an immediate short-lasting depression of the EEG and a tardive paroxysmal EEG activity. Both these phenomena were more relevant on the ipsilateral hemisphere. In some instances a tonico-clonic seizure was recorded.Pre-treatment with diazepam abolished the occurrence of the tardive EEG and behavioral modifications.In accord with previous findings, focal seizure activity is likely to be responsible for the metabolic abnormalities associated with osmotic opening of the BBB. This preparation therefore produces in the brain unphysiological states in respect to local metabolism and electrical function.     

Influence of exogenous NO donator and variations in the Ca<Superscript>2+</Superscript> content on transport activity related to tonoplast proton pumps in ontogenesis and under hyperosmotic stress

The changes in transport activity of tonoplast proton pumps under the influence of exogenous NO donator and modulation of Ca²⁺ concentration jointly and separately were investigated at different stages of ontogenesis and under hyperosmotic stress. The results suggest that both exogenous NO donator and Ca²⁺ ions can influence the activity of transport processes related to tonoplast and this influence is especially evident in the period of growth and accumulation of metabolites. Under hyperosmotic stress, H⁺-pyrophosphatase plays a more important role than H⁺-ATPase: the activity of the former increases 2.3-fold compared to the control osmotic conditions, whereas the activity of H⁺-ATPase is practically unchanged. H⁺-pyrophosphatase was more responsive to the presence of exogenous NO donator and to variations in Ca²⁺ concentration. The effects of exogenous NO donator on tonoplast proton pumps depended on the concentration of Ca²⁺, which apparently can mediate NO action.