Genotoxic effects of a sub-acute low-level inhalation exposure to a mixture of carcinogenic chemicals

A study was conducted using a combined testing protocol (CTP), to determine whether short-term biological end-points, singly or in combination, are sufficiently sensitive to identify damage induced by exposure to ambient levels of industrial chemicals. A small-scale inhalation set-up which is both economical and easy to assemble was designed. Mice were exposed to 4 concentrations of a custom-blend mixture of benzene, chloroprene, epichlorohydrin and xylene in a ratio of 2:2:1:2, respectively. The concentrations for benzene, chloroprene and xylene were 0, 0.1, 1.0 and 10 ppm each. Concentrations for epichlorohydrin were half those for the other components. Groups of 22 males and 22 female mice were exposed to each concentration of the mixture for 3 and 6 weeks. Selected biological end-points including urine mutagenesis, bone marrow cell aberrations and micronuclei, spleen lymphocyte aberrations and liver enzyme induction were monitored. The spleen lymphocyte aberrations and liver enzyme induction were the most sensitive end-points. The lymphocytes showed a significant induction of chromosome aberrations from exposure for 3 weeks to all 3 concentrations of the mixtures. After 6 weeks of exposure, significant induction of aberrations was observed after exposure to low and medium concentrations but not to the high concentration. This lack of response at the high concentration after 6 weeks exposure, appeared to correlate with a significant induction of glutathione S-transferase in the liver. Since this enzyme is known to detoxify 3 of the 4 chemicals in our mixture, it may indicate a detoxification mechanism after enzyme induction. The present study indicates that the CTP is sufficiently sensitive to identify toxicological effects after exposure to ambient levels of a gas mixture.     

A common precursor for a putative hemorrhagic protein and rhodostomin, a platelet aggregation inhibitor of the venom of Calloselasma rhodostoma: molecular cloning and sequence analysis.

Rhodostomin is a platelet aggregation inhibitor secreted by the venom gland of Calloselasma rhodostoma. We report here the isolation of a 1.67-kilobase (kb) lambda gt11 cDNA clone using degenerate oligonucleotide probe based on a partial amino acid sequence of rhodostomin. The amino acid sequence deduced from an open reading frame of the cDNA indicates that (i) the 68-amino acid sequence of rhodostomin is located at the carboxyl terminus of the precursor polypeptide and (ii) a peroxisomal targeting sequence (ser.his.ala.) exists between the stop codon and the rhodostomin sequence of the precursor. Since the amino-terminal segment of the deduced sequence shows a high degree of identity with hemorrhagic proteins, which are zinc-metalloproteinases, found in the venom of some crotalid and viperid snakes, our results also predict the existence of at least one such hemorrhagic protein in the venom of Calloselasma rhodostoma. The derivation of a platelet aggregation inhibitor and a hemorrhagic protein from the same precursor protein is consistent with the fact that these proteins may be synergistic in function.     

Encapsulation of Probiotics: Proper Selection of the Probiotic Strain and the Influence of Encapsulation Technology and Materials on the Viability of Encapsulated Microorganisms

Probiotic encapsulation is an entire system that not only involves but also depends on many factors. Elements such as the encapsulation method itself, materials, environmental conditions, and last, but not least, the strain; all play an important role in the encapsulation process. The current paper focuses on the right selection of probiotics, the various stress factors that impact the survival capacity of probiotics during and after encapsulation, and the rational selection of appropriate protection strategies to overcome these factors and achieve the highest possible encapsulation efficiency under optimal conditions. This review discusses the effects of temperature, moisture content, and water activity as well as pH, oxygen, and pressure on the viabilities of microorganisms. The effect of the surface and structure of the capsules on the encapsulated microorganisms and the impact of the materials used for the encapsulation are discussed as well. Last, but not least, the importance of choosing the right bacteria is reviewed.     

Digest: The evolution of sexual imprinting as an assortative mating mechanism*

In this issue, Yeh et al. (2018) investigated whether sexual imprinting could act as an assortative mating mechanism, reducing hybridization and increasing premating isolation. While they indeed find that imprinting leads to assortative mating and reduced hybridization, the strength at which imprinting evolves is usually intermediate, because it is counterbalanced by the costs of imprinting and the benefits of adaptive hybridization. Thus, while sexual imprinting can act as an assortative mating mechanism, it is often not the sole element of female mate choice.     

Nutrient scavenging activity and antagonistic factors of non-photobiont lichen-associated bacteria: a review

Lichens are defined as the specific symbiotic structure comprising a fungus and a green alga and/or cyanobacterium. Up until recently, non-photobiont endothallic bacteria, while known to be present in large numbers, have generally been dismissed as functionally irrelevant cohabitants of the lichen thallus, or even environmental contaminants. Recent analyses of lichen metagenomes and innovative co-culture experiments have uncovered a functionally complex community that appears to contribute to a healthy lichen thallus in several ways. Lichen-associated bacteriomes are typically dominated by several lineages of Proteobacteria, some of which may be specific for lichen species. Recent work has implicated members of these lineages in several important ecophysiological roles. These include nutrient scavenging, including mobilization of iron and phosphate, nitrogen fixation, cellulase, xylanase and amylase activities, and oxidation of recalcitrant compounds, e.g. aromatics and aliphatics. Production of volatile organic compounds, conferring antibacterial and antifungal activity, has also been demonstrated for several lichen-associated isolates. In the present paper we review the nature of non-phototrophic endolichenic bacteria associated with lichens, and give insight into the current state of knowledge on their importance the lichen symbiotic association.     

Membrane effects of aminoglycoside antibiotics measured in liposomes containing the fluorescent probe, 1-anilino-8-naphthalene sulfonate

The mechanism of membrane disturbance by aminoglycoside antibiotics was investigated in liposomes containing the fluorescent probe, 1-anilino-8-naphthalene sulfonate (ANS). Liposomes of PC and different anionic phospholipids (1:1 to 15:1 molar ratios) were challenged with aminoglycosides in the presence of low (1 microM) and high (3 mM) concentrations of calcium. Liposomes containing PIP2 showed the greatest drug-induced changes in ANS fluorescence in the presence of high and low concentrations of calcium and at all PC:PIP2 molar ratios tested. Liposomes containing other anionic phospholipids (PS, PI and PIP) were not reactive toward aminoglycosides in the presence of 3 mM calcium or when the ratio of PC to anionic lipid was increased to 10:1. The aminoglycoside-induced changes of ANS fluorescence were not due to any changes in the emission spectrum of ANS, nor to changes in quantum yield, nor to a change in the binding affinity of ANS. It is concluded that a specific aminoglycoside-PIP2 interaction results in phase separation of PC and PIP2 and thus increases the number of available ANS binding sites in PC:PIP2 liposomes.     

Measurement of inhibin and an index of inhibin production by rat testes during postnatal development

Our previous studies have shown that inhibin activity in rat testes can be measured using an in vitro inhibin bioassay. In animals that have undergone unilateral efferent duct ligation (EDL), the difference in inhibin content between the ligated and nonligated testis can be used as an index of the rate of inhibin production in vivo. In the present study we examined postnatal changes in inhibin content in the testes, and the production rates of inhibin and seminiferous tubule fluid in groups of neonatal, immature, and adult rats from 1 to 80 days old. We detected inhibin activity in testes of 1-day-old rats; the activity level rose linearly to Day 8, subsequently increasing markedly from Day 30 until it reached a plateau at Day 45. Increments in the content of inhibin and weight of the testis after unilateral EDL, interpreted to represent production of inhibin and seminiferous tubule fluid, commenced at Day 20 and increased rapidly between Days 30 and 50, decreasing thereafter to Day 80. The increase in content and production of inhibin was directly correlated to the rise in serum follicle-stimulating hormone (FSH) and testosterone, suggesting that these two hormones are important in controlling inhibin secretion. In addition, the changes in serum FSH from the high, postnatal levels to those typical of adults were inversely correlated to the content and production rate inhibin in the testes and concentrations of testosterone in the serum. These data support the hypothesis that inhibin is specifically involved in the feedback control of pituitary FSH secretion during postnatal development, although a role for testosterone or a synergistic interaction between the two hormones cannot be excluded.