Radiomodulatory effect of liposome encapsulated AK-2123 on tumor in mice exposed to hepatocarcinogen

An attempt was made to evaluate the whole body -radiation effect on tumor in the presence of free and liposome encapsulated AK-2123, a hypoxic cell radiosensitizer that has widely been used in combination with a number of cancer therapies such as thermotherapy, chemotherapy and radiotherapy. Entrapment efficiency of AK-2123 into liposome was determined by LASER Raman spectroscopy. Cancer induction in mice was carried out by repeated exposure of N-nitrosodiethylamine (DEN) in combination with partial hepatectomy. Parameters such as marker enzymes activities (GGT and AChE), rates of nucleic acid synthesis, viability modification factor and the histology of liver tissues monitored, supported the induction of cancer in liver. In addition, the effect of free as well as liposome encapsulated AK-2123 on haemopoietic parameters were also studied. It was observed that AK-2123 after incorporation into liposome afforded more efficient radiomodulatory effects than that of free AK-2123 as determined by the above-mentioned parameters. Neither free AK-2123 nor liposome encapsulated AK-2123 showed any detectable toxic effects on the mice. Thus, it is seen that treatment of cancer with a combination of radiation, a radiomodifier and a drug delivery system, opens a wide scope for exploitation for the improvement of existing cancer therapies. (Mol Cell Biochem 271: 139–150, 2005)     

Minimal CK2 activity required for yeast growth

Protein kinase CK2 is essential for the growth of Saccharomyces cerevisiae. Yeast cells that lack the functional genes coding for both the catalytic subunits of protein kinase CK2 can grow only if they are complemented by exogenous cDNAs coding for this subunit. A series of deletion mutants of CK2α from Xenopus laevis was constructed. These mutants that have carboxyl end deletions yield a CK2α product that varies over four orders of magnitude in its capacity to phosphorylate casein in vitro. Complementation of yeast RPG41-1a, a mutant defective in CKA1 and CKA2 genes, with wild-type X. laevis CK2α and with cDNAs coding for truncated CK2α having amino acids 1–328 and 1–327 resulted in cells that grew in gal-minimal media at 30 ^∘C as well as the cells harboring the yeast CKA2 gene. However, the growth was significantly diminished when cells were complemented with X. laevis CK2α containing 1–326 amido acids. This mutant has 0.6% of the catalytic activity of the wild-type enzyme. Yeast cells that expressed CK2α 1–324 and 1–323 which have 10-and 100-fold less activity, respectively, were not able to grow. The growth of cells containing the CK2α 1–326 mutant was very sensitive to temperature, and minimal growth was observed at 37 ^∘C. This mutant was also more sensitive to UV radiation but was not significantly affected by 0.4 M NaCl.Both authors contributed equally to this work     

Latitudinal characteristics of below- and above-ground biomass of Typha: a modelling approach

BACKGROUND AND AIMS: The latitudinal differences in the growth characteristics of Typha are largely unknown, although a number of studies have pointed out the effects of climate on the growth and productivity of Typha. Therefore, a dynamic growth model was developed for Typha to examine the effects of latitudinal changes in temperature and radiation on partitioning of the total biomass during the growing season into rhizomes, roots, flowering and vegetative shoots, and inflorescences. METHODS: After validating the model with data from growth studies of Typha found in past literature, it was used to investigate the dynamics of above- and below-ground biomasses at three latitudes: 30 degrees, 40 degrees and 50 degrees. KEY RESULTS: Regardless of the initial rhizome biomass, both above- and below-ground biomass values converged to a latitude-specific equilibrium produced by the balance between the total production and respiration and mortality losses. Above-ground biomass was high from 10 degrees to 35 degrees latitude with sufficient radiation, despite high metabolic losses; however, it decreased markedly at higher latitudes due to a low photosynthetic rate. Below-ground biomass, on the other hand, increased with latitude up to 40 degrees due to decreasing metabolic losses, and then markedly decreased at higher latitudes. Above-ground biomass was enhanced with an increasing number of cohorts regardless of latitude. However, although more cohorts resulted in a larger below-ground biomass at low latitudes, the largest below-ground biomass was provided by a smaller number of cohorts at high latitudes. This difference is due to low production rates of late-season cohorts in high latitudes, compared with consumption for shooting and establishing foliage. CONCLUSIONS: The model could be used to predict the potential growth of Typha in given conditions over a wide range of latitudes and is useful for practical applications such as wetland management or wastewater treatment systems using Typha.     

The effects of time,space and spectrum on auditory grouping in túngara frogs

Male túngara frogs (Physalaemus pustulosus) produce complex calls consisting of two components, a ~350 ms FM sweep called the “whine” followed by up to seven ~40 ms harmonic bursts called “chucks”. In order to choose and locate a calling male, females attending to choruses must group call components into auditory streams to correctly assign calls to their sources. Previously we showed that spatial cues play a limited role in grouping: calls with normal spectra and temporal structure are grouped over wide angular separations (≤135°). In this study we again use phonotaxis to first test whether an alternative cue, the sequence of call components, plays a role in auditory grouping and second, whether grouping is mediated by peripheral or central mechanisms. We found that while grouping is not limited to the natural call sequence, it does vary with the relative onset times of the two calls. To test whether overlapping stimulation in the periphery is required for grouping, the whine and chuck were filtered to restrict their spectra to the sensitivity ranges of the amphibian and basilar papillae, respectively. For these dichotic-like stimuli, grouping still occurred (albeit only to 45° separation), suggesting that stream formation is mediated by central mechanisms.     

Influence of near null magnetic field on in vitro growth of potato and wild Solanum species

The influence of near null magnetic field on in vitro growth of different cultures of potato and related Solanum species was investigated for various exposure times and dates. Potato (Solanum tuberosum L. cv. Désirée) in vitro cultures of shoot tips or nodal segments were used. Three different exposure periods revealed either stimulation or inhibition of root, stem, or leaf in vitro growth after 14 or 28 days of exposure. In one experiment the significant stimulation of leaf growth was also demonstrated at biochemical level, the quantity of chlorophyll a and b and carotenoids increasing more than two-fold. For the wild species Solanum chacoense, S. microdontum, and S. verrucosum, standardized in vitro cultures of nodal stem segments were used. Root and stem growth was either stimulated or slightly inhibited after 9 days exposure to near null magnetic field. Callus cultures obtained from potato dihaploid line 120/19 were maintained in near null magnetic field in 2 different months. For these experiments as well as for Solanum verrucosum, callus cultures recorded either slight inhibition or no effect on fresh weight. For all experiments significant growth variation was brought about only when geomagnetic activity (AP index) showed variations at the beginning of in vitro growth and when the explant had at least one meristematic tissue. Moreover longer maintenance in near null magnetic field, 28 days as compared to 14 days or the controls, can also make a difference in plant growth in response to geomagnetic field variations when static component was reduced to zero value. These results of in vitro plant growth stimulation by variable component of geomagnetic field also sustain the so-called seasonal "window" effect.     

Seasonal effect on tissue culture response and plant regeneration frequency from non-bombarded and bombarded immature scutella of barley (<Emphasis Type="Italic">Hordeum vulgare</Emphasis>) harvested from controlled environment

Scutella of immature embryos from two barley cultivars were used for cell culture and transformation. Explants were supplied by continuous growth of donor plants in a 2-week schedule under defined conditions at first plants were grown for 6–7 weeks in a growth chamber, followed by 10–13 weeks in a greenhouse with stringent control of temperature and light round the year. Strong seasonal variation in plant regeneration frequency was observed for both genotypes in non-bombarded (control) as well as bombarded and subsequent selected explants. Scutella from immature embryos of cv. Salome showed increased frequencies of plant regeneration from January to March, reaching highest values in March/April and followed by a continuous and strong decrease from May to December. This tendency was observed in all 3 years studied, although absolute numbers of plant regeneration varied between the years. The same seasonal effect was evident for plant regeneration from immature scutella of cv. Golden Promise. Frequency of embryogenic callus formation was also found to be influenced by season but this effect was not so pronounced as for plant regeneration.     

Diapause incidence in the two-spotted spider mite increases due to predator presence, not due to selective predation

We recently reported evidence for increased diapause incidence in the spider mite Tetranychus urticae in presence of the predatory mite Typhlodromus pyri. This effect may arise from (1) selective predation on non-diapause spider mites, (2) predator-induced diapause in spider mites, or (3) both. Using a different strain of T. urticae, we first recovered increased diapause incidence in association with predators. Then, we tested for selective feeding in two-choice experiments with equal numbers of non-diapause and diapause spider mites. We found that the predatory mite had a significant preference for the latter. This indicates that increased diapause incidence in association with predatory mites is not due to selective predation. Therefore, predator-mediated physiological induction of diapause seems a more likely explanation. The cues leading to induction appear to relate to the predators, not their effects, since predation simulated by spider-mite removal or puncturing did not significantly affect diapause incidence. Why spider mites benefit from this response, remains an open question.This revised version was published online in May 2005 with a corrected cover date.     

The use ofXenopus oocytes and embryos as a route towards cell replacement

When nuclei of somatic cells are transplanted to enucleated eggs ofXenopus, a complete reprogramming of nuclear function can take place. To identify mechanisms of nuclear reprogramming, somatic nuclei can be transplanted to growing meiotic oocytes ofXenopus, and stem cell genes activated without DNA replication. The combination of somatic cell nuclear transfer with morphogen signalling and the community effect may lead towards the possibility of cell replacement therapy. When mechanisms of nuclear reprogramming are understood, it may eventually be possible to directly reprogramme human somatic cell nuclei without the use of eggs.     

Shock wave treatment in medicine

Extracorporeal shock wave therapy in orthopedics and traumatology is still a young therapy method. Since the last few years the development of shock wave therapy has progressed rapidly. Shock waves have changed the treatment of urolithiasis substantially. Today shock waves are the first choice to treat kidney and urethral stones. Urology has long been the only medical field for shock waves in medicine. Meanwhile shock waves have been used in orthopedics and traumatology to treat insertion tendinitis, avascular necrosis of the head of femur and other necrotic bone alterations. Another field of shock wave application is the treatment of tendons, ligaments and bones on horses in veterinary medicine. In the present paper we discuss the basic theory and application of shock waves and its history in medicine. The idea behind using shock wave therapy for orthopedic diseases is the stimulation of healing in tendons, surrounding tissue and bones. This is a completely different approach compared to urology where shock waves are used for disintegration     

A model for radiation-induced bystander effects, with allowance for spatial position and the effects of cell turnover

Bystander effects, whereby cells that are not directly exposed to ionizing radiation exhibit adverse biological effects, have been observed in a number of experimental systems. A novel stochastic model of the radiation-induced bystander effect is developed that takes account of spatial location, cell killing and repopulation. The ionizing radiation dose- and time-responses of this model are explored, and it is shown to exhibit pronounced downward curvature in the high dose-rate region, similar to that observed in many experimental systems, reviewed in the paper. It is also shown to predict the augmentation of effect after fractionated delivery of dose that has been observed in certain experimental systems. It is shown that the generally intractable solution of the full stochastic system can be considerably simplified by assumption of pairwise conditional dependence that varies exponentially over time.