Metabolic state and cell cycle as determinants of facilitated uptake of genetic information by yeast <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

The transformation efficiency of yeast cells during exponential growth might be characterised as undulatory. The aim of the study was to investigate the reason for the fluctuation in transformation efficiency of yeast Saccharomyces cerevisiae p63-DC5 cells during exponential growth. The heightened response to exogenous DNA was observed with the growing yeast culture when budded cells were predominant. To confirm this phenomenon we carried out synchronization of yeast cells with 10 mM hydroxyurea. Results showed that synchronous yeast cells in the S-phase of cell cycle have enhanced transformation efficiency. Furthermore, S. cerevisiae p63-DC5 cells in the S-phase were successfully transformed with plasmid pl13 in the absence of lithium acetate. We indicated that the permeability of yeast cells in the S-phase to tetraphenylphosphonium (TPP) cations was significantly higher than in asynchronous culture. The results of our study showed that the fluctuation in transformation efficiency was strictly dependent on the metabolic state of yeast cells and the capacity of the yeast cells to become competent was related to the S-phase of cell cycle.     

Effect of Training and Match Loads on Hamstring Passive Stiffness in Professional Soccer Players

Objective:the purpose of this study was to identify differences in hamstring passive stiffness between the pre-season and in-season periods.Methods:Hamstring strength and passive stiffness were measured in professional male soccer players before and after the pre-season (4 weeks), and after the in-season (6 weeks) periods using an isokinetic dynamometer. Muscle passive stiffness was determined from the slope of the passive torque–angle relationship. External loads (acceleration and jumps) were monitored by GPS and internal loads by questionnaire.Results:Hamstring passive stiffness increased after 10 weeks of training and matches, without changes in passive peak torque and range of motion. The hamstring passive stiffness modifications were associated with the volume and intensity of accelerations and jumps. The individual data analysis also provided some support for the suppression of the biomechanical adaptation in the subjects with relatively large external load.Conclusions:Regular training and match workouts increase hamstring passive stiffness in professional soccer players but the adaptation of muscle-tendon unit passive elements might not occur if players experience excessive mechanical stress.     

Sex-Dependent Psychoneuroendocrine Effects of THC and MDMA in an Animal Model of Adolescent Drug Consumption

Ecstasy is a drug that is usually consumed by young people at the weekends and frequently, in combination with cannabis. In the present study we have investigated the long-term effects of administering increasing doses of delta-9-tetrahydrocannabinol [THC; 2.5, 5, 10 mg/kg; i.p.] from postnatal day (pnd) 28 to 45, alone and/or in conjunction with 3,4-methylenedioxymethamphetamine [MDMA; two daily doses of 10 mg/kg every 5 days; s.c.] from pnd 30 to 45, in both male and female Wistar rats. When tested one day after the end of the pharmacological treatment (pnd 46), MDMA administration induced a reduction in directed exploration in the holeboard test and an increase in open-arm exploration in an elevated plus maze. In the long-term, cognitive functions in the novel object test were seen to be disrupted by THC administration to female but not male rats. In the prepulse inhibition test, MDMA-treated animals showed a decrease in prepulse inhibition at the most intense prepulse studied (80 dB), whereas in combination with THC it induced a similar decrease at 75 dB. THC decreased hippocampal Arc expression in both sexes, while in the frontal cortex this reduction was only evident in females. MDMA induced a reduction in ERK1/2 immunoreactivity in the frontal cortex of male but not female animals, and THC decreased prepro-orexin mRNA levels in the hypothalamus of males, although this effect was prevented when the animals also received MDMA. The results presented indicate that adolescent exposure to THC and/or MDMA induces long-term, sex-dependent psychophysiological alterations and they reveal functional interactions between the two drugs.     

Operant model of frustrated expected reward in mice

One aspect of the addictive process that has not been thoroughly investigated is the consequence of the frustrated state occurring when the drug is not available. The present study aimed to validate a novel operant model of frustrated expected reward in mice. C57BL/6J mice were trained in operant conditioning maintained by chocolate-flavoured pellets or cocaine. After the completion of high rates of responding on a progressive ratio schedule, the reward was unexpectedly withheld. The consequences of this frustrated behaviour on anxiety, aggressiveness, perseveration, extinction and reinstatement were investigated. Mice exposed to the frustrated event perseverated in the operant responses and showed increased aggressiveness in the resident-intruder test. These animals also showed higher rates of cue-induced reinstatement of drug seeking. The present study provides a reliable operant model in mice to evaluate a frustrated state following reward unavailability. This animal model could be useful to study the behavioural and neurochemical consequences related to the emotional states generated during the omission of a highly expected reward.     

Semi-Supervised Morphosyntactic Classification of Old Icelandic

We present IceMorph, a semi-supervised morphosyntactic analyzer of Old Icelandic. In addition to machine-read corpora and dictionaries, it applies a small set of declension prototypes to map corpus words to dictionary entries. A web-based GUI allows expert users to modify and augment data through an online process. A machine learning module incorporates prototype data, edit-distance metrics, and expert feedback to continuously update part-of-speech and morphosyntactic classification. An advantage of the analyzer is its ability to achieve competitive classification accuracy with minimum training data.     

Positron emission tomographic imaging of the cannabinoid type 1 receptor system with [¹¹C]OMAR ([¹¹C]JHU75528): improvements in image quantification using wild-type and knockout mice

In this study, we assessed the feasibility of using positron emission tomography (PET) and the tracer [11C]OMAR ([11C]JHU75528), an analogue of rimonabant, to study the brain cannabinoid type 1 (CB1) receptor system. Wild-type (WT) and CB1 knockout (KO) animals were imaged at baseline and after pretreatment with blocking doses of rimonabant. Brain uptake in WT animals was higher (50%) than in KO animals in baseline conditions. After pretreatment with rimonabant, WT uptake lowered to the level of KO animals. The results of this study support the feasibility of using PET with the radiotracer [11C]JHU75528 to image the brain CB1 receptor system in mice. In addition, this methodology can be used to assess the effect of new drugs in preclinical studies using genetically manipulated animals.     

Tetraphenylphosphonium inhibits oxidation of physiological substrates in heart mitochondria

We show that tetraphenylphosphonium inhibits oxidation of palmitoylcarnitine, pyruvate, malate, 2-oxoglutarate and glutamate in heart mitochondria in the range of concentration (1–5 µM) commonly used for the determination of mitochondrial membrane potential. The inhibition of 2-oxoglutarate (but not other substrate) oxidation by tetraphenylphosphonium is dependent on the concentration of 2-oxoglutarate and on extramitochondrial free calcium, and the kinetic plots are consistent with a mixed type of inhibition. Our results indicate that tetraphenylphosphonium interacts with enzymes, specifically involved in the oxidation of 2-oxoglutarate, most possibly, 2-oxoglutarate dehydrogenase.     

Li+ effect on the cell wall of the yeast Saccharomyces cerevisiae as probed by FT-IR spectroscopy

The effect of Li⁺ ions as a transformation inducing agent on the yeast cell wall has been studied. Two Saccharomyces cerevisiae strains, p63-DC5 with a native cell wall, and strain XCY42-30D(mnn1) which contains structural changes in the mannan-protein complex, were used. Fourier transform infrared (FT-IR) spectroscopy has been used for the characterization of the yeast strains and for determination of the effect of lithium cations on the cell wall. A comparison of the carbohydrate absorption band positions in the 970–1185 cm^?1 range, of Na⁺ and Li⁺ treated yeast cells has been estimated. Absorption band positions of the cell wall carbohydrates of p63-DC5 were not influenced by the studied ions. On the contrary, the treatment of XCY42-30D(mnn1) cells with Li⁺ ions shifted glucan band positions, implying that the cell wall structure of strain XCY42-30D(mnn1) is more sensitive to Li⁺ ion treatment.