The Functional Significance of Bacterial Predators

Predation structures food webs, influences energy flow, and alters rates and pathways of nutrient cycling through ecosystems, effects that are well documented for macroscopic predators. In the microbial world, predatory bacteria are common, yet little is known about their rates of growth and roles in energy flows through microbial food webs, in part because these are difficult to quantify. Here, we show that growth and carbon uptake were higher in predatory bacteria compared to nonpredatory bacteria, a finding across 15 sites, synthesizing 82 experiments and over 100,000 taxon-specific measurements of element flow into newly synthesized bacterial DNA. Obligate predatory bacteria grew 36% faster and assimilated carbon at rates 211% higher than nonpredatory bacteria. These differences were less pronounced for facultative predators (6% higher growth rates, 17% higher carbon assimilation rates), though high growth and carbon assimilation rates were observed for some facultative predators, such as members of the genera Lysobacter and Cytophaga, both capable of gliding motility and wolf-pack hunting behavior. Added carbon substrates disproportionately stimulated growth of obligate predators, with responses 63% higher than those of nonpredators for the Bdellovibrionales and 81% higher for the Vampirovibrionales, whereas responses of facultative predators to substrate addition were no different from those of nonpredators. This finding supports the ecological theory that higher productivity increases predator control of lower trophic levels. These findings also indicate that the functional significance of bacterial predators increases with energy flow and that predatory bacteria influence element flow through microbial food webs.IMPORTANCE The word "predator" may conjure images of leopards killing and eating impala on the African savannah or of great white sharks attacking elephant seals off the coast of California. But microorganisms are also predators, including bacteria that kill and eat other bacteria. While predatory bacteria have been found in many environments, it has been challenging to document their importance in nature. This study quantified the growth of predatory and nonpredatory bacteria in soils (and one stream) by tracking isotopically labeled substrates into newly synthesized DNA. Predatory bacteria were more active than nonpredators, and obligate predators, such as Bdellovibrionales and Vampirovibrionales, increased in growth rate in response to added substrates at the base of the food chain, strong evidence of trophic control. This work provides quantitative measures of predator activity and suggests that predatory bacteria-along with protists, nematodes, and phages-are active and important in microbial food webs.

Influence of CYP2D6 and CYP2C19 genetic polymorphism on the pharmacokinetics of tolperisone in healthy volunteers

PURPOSE

This is the first study that connects pharmacokinetics of tolperisone with genetic polymorphism of the enzymes involved in its metabolism in human. We aimed to identify the influence of polymorphism of two main enzymes (CYP2D6 and CYP2C19) on pharmacokinetic profile of parent drug.

METHODS

In a single-dose study, 28 healthy Caucasian male volunteers received an oral dose of 150 mg of tolperisone. The subjects were genotyped with respect to CYP2D6 and CYP2C19 enzymes. Plasma was sampled for up to 12 h post dose, followed by quantification of tolperisone by a fully validated HPLC-tandem mass spectrometry (MS/MS) method. The pharmacokinetic parameters were estimated using a non-compartmental method and compared statistically at level p < 0.05 across the genotyped groups.

RESULTS

High variability (exceeded 100%) of main bioavailability parameters (AUCt, AUC(inf), C(max)) was observed in the whole group of subjects. An essential difference in the pharmacokinetics of tolperisone of quick metabolizers whose genotype expressed wild homozygote CYP2D6 *1/*1 with respect to heterozygous *1/*4 and *1/*5 subjects was demonstrated. The mean AUC(inf) was 2.1- and 3.4-fold higher in *1/*4 and *1/*5, respectively, than in *1/*1 subjects. In case of Cmax, the differences were greater and reached maximally 3.8 times (mean values 54.00, 98.85, and 205.20 ng/mL for CYP2D6 *1/*1, *1/*4, and *1/*5, respectively). Values of the parameters for the one subject that expressed *4/*4 genotype were even 8.5 times higher than in subjects with extensive or intermediate phenotype. Although CYP2C19 *1/*2 subjects had higher AUCt, AUC(inf), and Cmax values than *1/*1, no statistically significant differences were observed. Oral clearance (CL/F) significantly decreased by 65.7% in heterozygous *1/*2 relative to homozygous *1/*1 extensive metabolizers.

CONCLUSION

In this study, we first demonstrated the effect of CYP2D6 polymorphism on pharmacokinetics of tolperisone in Caucasian subjects. The contribution of CYP2C19 enzyme seems to be less important.

[The effect of selenium and vitamin E on the healing process of experimental corneal lesions in the eye of the rabbit]

PURPOSE

Evaluation of antioxidants: selenium and vitamin E efficacy in the treatment of experimental corneal lesion.

MATERIAL AND METHODS

Solution of selenium in 0.9% NaCl, concentration 0.01 g/L, to which vitamin E was added to obtain suspension of 2.5 g/L was used in 9 rabbits. The cornea was damaged by removing the epithelium from the central area of 7 mm diameter. To the right eye selenium solution with vitamin E was instilled.

RESULTS

In two eyes in which antioxidants were used evident prompt healing of corneal ulceration was noticed. Mean lesion diameter in eyes treated with antioxidants was: on 1st day 5.44 mm, in 2nd day 1.61 mm and on the 3rd day 0.33 mm. In control eyes diameters were: 6.67 mm, 2.28 mm and 0.56 mm, respectively.

CONCLUSIONS

Solution used in our study was tolerated very well. Faster healing process was noticed in eyes where antioxidants were used.

[Gentamicin kinetics in the blood and aqueous humor of the rabbit eye after intramuscular and subconjunctival administration]

Investigations were performed in rabbits which were given gentamycin intramuscularly and subconjunctivally. After subconjunctival application gentamycin passes quickly into the eye and its therapeutical level persists up to 1 hour. After intramuscular injection gentamycin is passing slower into the aqueous but persists there longer (the therapeutical level--up to 5.5 hours).

[Bioavailability of drugs applied to the eye externally]

There are following forms of the most frequently used ocular therapeutics: eye drops, ointments and inserts. In dependence on the physico-chemical properties of the therapeutical substance and the kind of disease one has to formulate the form of the drug in the manner to obtain its maximal bioavailability. By increasing their viscosity one can keep the watery solutions in the conjunctival sac for around 60 min. The time of the contact of the drug given in the form of suspension is limited mainly by the viscosity of the solution and the size of the molecules suspended in it. The ointments stay on the surface of the eye up to 2 hours. The ocular inserts secure a steady flow of the therapeutical substance up to 7 days. The compounds penetrate to the anterior chamber aqueous mainly through the cornea. Therefore the physiological factors of the lacrimal fluid, the properties of the cornea are influencing the penetration of the corneo-chamber barrier by the therapeutical substance.

Correlation between the total cholesterol serum concentration data and carbamazepine steady-state blood levels in humans

The purpose of this study was to investigate the pharmacokinetics of carbamazepine at steady state, after multiple doses in patients with elevated serum cholesterol levels. Twelve patients participated in the investigation; patients were divided into two groups according to their total serum cholesterol levels. Each patient received multiple doses of carbamazepine 600 mg po once per day. Blood samples were collected and analyzed for carbamazepine by gas-liquid chromatography. The clearance concept was used to describe the pharmacokinetic behavior of carbamazepine in high and low cholesterol patients. The area under the plasma concentration-time curve was determined by the trapezoidal rule method. This value was used to determine the oral dose clearance. In this study, the authors found that the elevated serum cholesterol and elevated total lipids cause a decrease in drug concentration. The significantly higher values of the total body clearance of carbamazepine, obtained in patients with elevated serum cholesterol levels, may have significance in clinical practice.