Glucose transport and metabolism in cultured human skin fibroblasts

Human skin fibroblast cultures, seeded at $\text{10}{}^5\text{cells}\text{5}\text{cm}$ plate and allowed to grow to confluence at approx. $\text{10}{}^6\text{cells}\text{5}\text{cm}$ plate, utilized a glycolytic mode of metabolism where the ratio of glucose utilized to lactate produced wa 0.62±0.05 (Zielke, R.H., Ozand, P.T., Tyldon, J.I., Sevdalian, D.A. and Cornblath, M. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 4110–4114) (mean±S.E.). When the glucose in the medium was exhausted, the lactate produced during the highly glycolytic phase was then reutilized. In monolayer cultures that had been washed with phosphate-buffered saline, rates of glucose utilization were measured at 0.25 and 2 mM glucose by monitoring the appearance of ³H₂O from [5-³H]glucose. Rate of utilization for each concentration of glucose decreased markedly as the cultures became more confluent. This decrease also correlated with a reduced ability to transport glucose as measured by 2-deoxy-[³H]glucose uptake in washed monolayer cultures. In washed confluent culture of fibroblasts, glucose utilization was markedly decreased by the presence of pyruvate and lactate but not by glutamine. The respiratory inhibitors, rotenone and antimycin, did not increase the rate of glucose utilization except when added in combination with pyruvate. We conclude that cultured skin fibroblasts posses a highly glycolytic mode of metabolism but that this mode can become more oxidative in the presence of sufficient quantities of pyruvate and lactate.     

Differential expression of β-glucosidase in tomato — stress stimuli systems

In the present work the responses of β-glucosidase in leaves of tomato plants subjected to various stress factors of both pathogenic (fungi, bacteria, viruses) and abiotic origin (heat shock) were studied. Biochemical and cytochemical methods were applied. It was established that an increase of β-glucosidase activity is induced uniquely by fungal pathogens. The cytochemical tests confirm the finding. Hence, the conclusion can be drawn that β-glucosidase response is a specific character of fungal pathogenesis in tomato; probably, the enzyme is involved in plant — fungi recognition. The data are in accordance with our previous results on tobacco and wheat — stress stimuli systems.     

Gibberellins and light synergistically promote somatic embryogenesis from the in vitro apical root sections of spinach

Plant Cell, Tissue and Organ Culture (PCTOC) - Gibberellins (GAs) play a pivotal role in the induction of somatic embryogenesis from in vitro root apices of spinach plants. With the aim to...     

Comparison of blood pro/antioxidant levels before and after acute exercise in athletes and non-athletes

The aims of our study were to assess the redox state of adolescent athletes and non-athletes both at rest and after acute exposure to physical load and to find relations between parameters of redox state and morphofunctional characteristics of subjects. 58 young handball players and 37 non-athletes were subjected to body composition analysis, measuring of maximal oxygen consumption and blood sampling immediately before and after a maximal progressive exercise test. At rest, athletes had significantly higher superoxide dismutase (SOD) and catalase (CAT) activity, higher levels of glutathione (GSH) and nitric oxide (NO) and lower levels of lipid peroxidation (TBARS) compared with non-athletes. A maximal exercise test induced statistically significant rise of superoxide anion radical (O2-), hydrogen peroxide (H2O2) and NO levels in non-athletes, while TBARS levels decreased. Athletes experienced the fall in NO levels and the fall in CAT activity. After exercise, athletes had significantly lower levels of O2- compared with non-athletes. Two way repeated measures ANOVA showed that the response of O2-, NO and TBARS to the exercise test was dependent on the sports engagement (training experience) of subjects. Significant correlations between morphofunctional and redox parameters were found. These results suggest that physical fitness affects redox homeostasis.     

Regeneration of interspecific somatic hybrids between Helianthus annuus L. and Helianthus maximiliani (Schrader) via protoplast electrofusion

Helianthus maximiliani is one of the wild Helianthus species with the genes for resistance to many pathogens including Sclerotinia sclerotiorum. Unfortunately, a transfer of disease resistance genes from this species into the cultivated sunflower is limited by its poor crossability with the cultivated sunflower and sterility of interspecific hybrids. To overcome this problem, mesophyll protoplasts of Sclerotinia sclerotiorum-resistant clone of H. maximiliani were electrically fused with etiolated hypocotyl protoplasts of the cultivated sunflower inbred line PH-BC₁-91A. Fusion products were embedded in agarose droplets and subjected to different regeneration protocols. Developed microcalluses were released from the agarose and transferred into solid media. Shoot regeneration was achieved by culture of calluses on regeneration medium containing 2.2 mg l⁻¹ BAP and 0.01 mg l⁻¹ NAA after the treatment with a high concentration of 2,4 D for a limited period of time. A morphological and RAPD analysis confirmed a hybrid nature of the regenerated plants.     

Lactic acid bacteria and yeasts in kefir grains and kefir made from them

In an investigation of the changes in the microflora along the pathway: kefir grains (A)→kefir made from kefir grains (B)→kefir made from kefir as inoculum (C), the following species of lactic acid bacteria (83–90%) of the microbial count in the grains) were identified: Lactococcus lactis subsp. lactis, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus helveticus, Lactobacillus casei subsp. pseudoplantarum and Lactobacillus brevis. Yeasts (10–17%) identified were Kluyveromyces marxianus var. lactis, Saccharomyces cerevisiae, Candida inconspicua and Candida maris. In the microbial population of kefir grains and kefir made from them the homofermentative lactic streptococci (52–65% and 79–86%, respectively) predominated. Within the group of lactobacilli, the homofermentative thermophilic species L. delbrueckii subsp. bulgaricus and L. helveticus (70–87% of the isolated bacilli) predominated. Along the pathway A→B→C, the streptococcal proportion in the total kefir microflora increased by 26–30% whereas the lactobacilli decreased by 13–23%. K. marxianus var. lactis was permanently present in kefir grains and kefirs, whereas the dominant lactose-negative yeast in the total yeast flora of the kefir grains dramatically decreased in kefir C. Journal of Industrial Microbiology & Biotechnology (2002) 28, 1–6 DOI: 10.1038/sj/jim/7000186 Received 02 August 2000/ Accepted in revised form 15 July 2001     

Investigations of mannan and glucan in the cell wall ofCandida boidinii cultivated on methanol

The polysaccharide components (mannan and glucan) in the cell wall ofCandida boidinii M 363 grown on methanol and glucose as control were investigated using electron microscopy, cytochemical and biochemical methods. An ultrastructural rearrangement of the polymers in the cell wall of yeasts cultivated on methanol in comparison to those cultivated on glucose was established. The morphological changes correlate to the quantitative changes in the polysaccharide constituents of the cell wall. The forming and the role of thiosemihydrocarbazide (TSHC) — negative zones in theCandida boidinii cell wall cultivated on methanol media are discussed.     

Physico-chemical characterization of exomannan from <Emphasis Type="Italic">Rhodotorula acheniorum</Emphasis> MC

The batch fermentation of Rhodotorula acheniorum MC on a culture medium containing 5% sucrose, mineral salts and yeast extract at 26 °C for 96 h, with aeration at 0.75 v/v/m and agitation at 500 rev min ⁻¹ resulted in the synthesis of an exopolysaccharide (6.2 g l ⁻¹) which formed two fractions upon precipitation. The fractions were purified to a carbohydrate content of 98.2% for fraction I and 87.3% for fraction II. Mannose was the main monosaccharide component in a 92.8% concentration in fraction I and a 90.6% concentration in Fraction II. The exopolysaccharide was thus a mannan. The gel chromatograms confirmed the chemical composition of both fractions. The molecular weight of mannan I was 310 kD, whereas that of mannan II was 249 kD. The mannan I intrinsic viscosity [η]=6.23 dl g⁻¹ was higher than that of mannan II [η]=2.73 dl g⁻¹. The water-binding capacity of the mannan samples was established within the 1.2–3.5 g g⁻¹ range. The multiplicative model [η]=387.22. D_r^−0.1913. T^−1.095. C^1.814 describing the effect of the velocity gradient D_r, the exomannan concentration C and the temperature T on the dynamic viscosity values η of polymer solutions was obtained.     

Mutant Hansenula polymorpha strain with constitutive alcohol oxidase and peroxisome biosynthesis

A mutant of the methylotrophic yeast Hansenula polymorpha with constitutive alcohol oxidase (AOX) and peroxisome biosynthesis was obtained after UV treatment followed by cell plating on a medium containing methanol and 2-deoxy-D-glucose (DOG). DOG-resistant colonies of mutants were insensitive to catabolic repression by glucose and methanol. A selection procedure is described that allows the isolation of a mutant exhibiting a constitutive phenotype of AOX involved in methanol utilization. Furthermore, additional features of the constitutive presence of peroxisomes are demonstrated. 562 DOG-resistant colonies were tested, 24 of them demonstrating constitutive AOX formation. Based on quantitative analysis, one of the strains--DOG-13 was selected and its growth, biochemical and ultrastructural characteristics were examined. Its specific enzyme activity when cultivated on a yeast nitrogen base + 1% glucose (YNB + 1% Glucose) was found to reach 145 nmol x min(-1) x mg(-1) protein (compared to zero of the parent strain) after he 20th hour of cultivation. This was confirmed by fine-structure analysis, showing typical peroxisomes, which number and size increased with the enzyme activity. This study demonstrates a constitutive AOX and peroxisome biosynthesis by the mutant strain H. polymorpha DOG-13 obtained.