Muscular strength and jumping performance relationships in young women athletes

The relationships between muscular strength and vertical jumping performance were examined in young women (14-19 years) track and field jumpers (n = 20) and volleyball players (n = 21). The knee extensor muscular strength measured at 9 knee angles was correlated with jumping height and peak power at the squat (SJ) and the countermovement (CMJ) vertical jump tests. Pearson product coefficient of correlation was used to test the significance of these relationships (p 0.80). Specifically, in the volleyball players, the strong relationships were noted for muscular strength at the knee angle range of 40 degrees to 90 degrees and CMJ jumping height as well as SJ peak power. Results indicate the dissimilarity in the relationships between the knee extensor muscular strength and jumping performance in the young female track and field jumpers and volleyball players. In addition, it appears that the measure selected to evaluate jumping performance alters the correlational results.     

Acute protection of ischemic heart by FGF-2: involvement of FGF-2 receptors and protein kinase C

We examined the effect of fibroblast growth factor (FGF)-2 on myocardial resistance to injury when administered after the onset of ischemia, in vivo and ex vivo, and the role of FGF-2 receptors and protein kinase C (PKC). FGF-2 was injected into the left ventricle of rats undergoing permanent surgical coronary occlusion leading to myocardial infarction (MI). After 24 h, FGF-2-treated hearts displayed significantly reduced injury, determined by histological staining and troponin T release, and improved developed pressure compared with untreated controls. An FGF-2 mutant with diminished affinity for the tyrosine kinase FGF-2 receptor 1 (FGFR1) was not cardioprotective. FGF-2-treated hearts retained improved function and decreased damage at 6 wk after MI. In the ex vivo heart, FGF-2 administration during reperfusion after 30-min ischemia improved functional recovery and increased relative levels of PKC subtypes alpha, epsilon, and zeta in the particulate fraction, in a chelerythrine-preventable mode; it also decreased loss of energy metabolites. We conclude that intramyocardial FGF-2 administration shortly after the onset of ischemia confers protection from acute and chronic cardiac dysfunction and damage; FGF-2 delivered during reperfusion protects from ischemia-reperfusion injury; and protection by FGF-2 requires intact binding to FGFR1 and is likely mediated by PKC.     

Changes in size and composition of pigweed (Amaranthus hybridus L.) calcium oxalate crystals under CO2 starvation conditions

The functional role(s) of plant calcium oxalate (CaOx) crystals are still poorly understood. Recently, it was shown that crystals function as dynamic carbon pools whose decomposition could provide CO₂ to photosynthesis when stomata are closed (e.g. under drought conditions) and CO₂ starvation conditions may be created within the mesophyll. This biochemical process, named as ‘alarm photosynthesis’, can become crucial for plant survival under adverse conditions. Here, we study crystal decomposition under controlled CO₂ starvation conditions (either in the shoot or in the root) to obtain a better insight into the process of crystal formation and function. Hydroponically grown pigweed plants were kept in CO₂‐free air and/or CO₂‐free nutrient medium for 9 days. Crystal volume was monitored daily, and carbon stable isotope composition (δ¹³C) and Fourier transformation Raman spectra were obtained at the end of the experiment. A considerable reduction in the leaf crystal volume was observed in shoot‐CO₂‐starved plants at the end of the experiment. The smallest crystals were isolated from the plants in which carbon was excluded from both the shoot and the root and contained potassium nitrate. Crystal δ¹³C of CO₂‐starved plants was altered in a predicted way. Specifically, it depended on the average calculated isotope fractionation of all carbon fixation processes considered to be contributing in each experimental treatment. The results of the present study confirmed the correlation between CO₂ starvation conditions and the CaOx crystal decomposition. Inorganic carbon fixed in the root may represent a major carbon source for CaOx formation.     

Connexin 43 phosphorylation and degradation are required for adipogenesis

Connexin-43 (Cx43) is a membrane phosphoprotein that mediates direct inter-cellular communication by forming gap junctions. In this way Cx43 can influence gene expression, differentiation and growth. Its role in adipogenesis, however, is poorly understood. In this study, we established that Cx43 becomes highly phosphorylated in early adipocyte differentiation and translocates to the plasma membrane from the endoplasmic reticulum. As preadipocytes differentiate, Cx43 phosphorylation declines, the protein is displaced from the plasma membrane, and total cellular levels are reduced via proteosomal degradation. Notably, we show that inhibiting Cx43 degradation or constitutively over-expressing Cx43 blocks adipocyte differentiation. These data reveal that transient activation of Cx43 via phosphorylation followed by its degradation is vital for preadipocyte differentiation and maturation of functional adipocytes.     

Effect of cocaine and crack on the ploidy status of <Emphasis Type="Italic">Tetrahymena pyriformis</Emphasis>: a study using DNA image analysis

The effect of cocaine and crack on the ploidy status of Feulgen-stained Tetrahymena pyriformis macronuclei using computerized DNA image analysis system was tested. For this purpose, selected doses of 5, 10 and 20 μg (per mL culture) of both drugs were administered for 2, 5 and 20 h to protozoa cultures and DNA image analysis of T. pyriformis nuclei was performed. The analysis was based on the measurement of the following parameters: Ploidy Balance (PB), Degree of Aneuploidy (DA), skewness and kurtosis. The results have shown a positive effect of both cocaine and crack on PB and on DA of T. pyriformis macronuclei. In particular, our results reveal that the aneugenic effect (which is expressed as a decrease in PB and an increase in DA) of cocaine on T. pyriformis macronuclei follows a dose-dependent manner, while crack induces aneuploidy in a dose-independent manner. Changes in the PB and DA values would induce a disturbance in the cellular density and heterogeneity of chromatin and the increase in skewness and kurtosis values after exposure of T. pyriformis to both drugs, did confirm this hypothesis. These observations were further correlated with alterations in the chromosomal segregation and with damage in mitotic spindle microtubules observed previously. In this study the impact of cocaine and crack on genomic instability and carcinogenesis was further supported and T. pyriformis can be proposed as a model organism to test the nuclear ploidy status after exposure to harmful chemicals and drugs.     

Administration of FGF-2 to the heart stimulates connexin-43 phosphorylation at protein kinase C target sites

Fibroblast growth factor-2 (FGF-2) confers acute, preconditioning-like cardiac resistance to ischemic injury in a protein kinase C (PKC)-dependent fashion. One of the downstream targets of PKC is the gap junction protein connexin-43 (Cx43). We thus examined the effects of FGF-2 on Cx43 phosphorylation at specific PKC sites in the adult heart. Rat hearts perfused ex vivo for 20 min with an FGF-2-containing solution displayed increased levels of phosphorylated 44-45 kDa Cx43, assessed by western blotting. In addition, FGF-2 significantly upregulated phosphorylation of the PKC target serines 262 and 368 on Cx43 at intercalated disks, assessed using phosphospecific antibodies in immunolocalization and western blotting assays. Our data show that FGF-2, administered by perfusion, can alter the phosphorylation status of Cx43 at cardiomyocyte intercalated disks, and suggest a link between phosphorylation of Cx43 at specific PKC sites and FGF-2 cardioprotection.     

Synthesis of a second generation chroman/catechol hybrids and evaluation of their activity in protecting neuronal cells from oxidative stress-induced cell death

A new generation of chroman/catechol hybrids bearing heterocyclic five-membered rings, such as 1,2,4-oxadiazole 1,3,4-oxadiazole, 1,2,3-triazole, tetrazole and isoxazole, were designed and synthesized. The activity of the new derivatives against oxidative stress induced neuronal damage, was evaluated using glutamate-challenged hippocampal HT22 cells.Compound 3 in which a 3,4-dimethoxyphenyl moiety, is directly attached to the 1,2,4-oxadiazole ring was the most active among the 2-substituted chroman analogues, with EC₅₀ = 254 ± 65 nM. Concerning the 5-subtituted chroman analogues, isoxazole derivative 29 exhibited the strongest activity (EC₅₀ = 245 ± 38 nM). However, 29 was cytotoxic at concentrations higher than 1 μM, while the triazole analogue 24 (EC₅₀ = 801 ± 229 nM), was non-toxic at all concentrations tested.     

The carboxy-tail of connexin-43 localizes to the nucleus and inhibits cell growth

Gap junctions are plasma membrane intercellular communication channels that in addition to ensuring electrical coupling and coordinated mechanical activity, can act as growth suppressors. To define the role of a non-channel forming domain of connexin-43 (Cx43), the main constituent of cardiomyocyte gap junctions, on growth regulation, we expressed its C-terminal portion (CT-Cx43) in cardiomyocytes and HeLa cells. In addition to broad cytoplasmic localization, CT-Cx43 was also localized to the nucleus of both cell types, detected by immunofluorescence as well as immunoblotting of subcellular fractions. Furthermore, stable expression of CT-Cx43 in HeLa cells induced a significant decrease in proliferation. It is therefore suggested that plasma membrane localization and formation of channels are not required for growth inhibition by Cx43, and that nuclear localization of CT-Cx43 may exert effects on gene expression and growth.