Effects of repeated short-term cold exposures on cold induced thermogenesis of women

The effects of repeated exposures to resting cold air (10°C) on the shivering and thermogenic responses of women to standard cold stress were investigated. Ten women, aged 18 to 34 years, were divided into two groups of five women each. One group, the acclimated (A) was exposed ten times within 2 weeks, the first and the last exposures being the pre-and post-tests respectively. The second group, the control (C) was exposed twice within 18 days. Measurements of rectal and skin temperatures, oxygen uptake, time to onset of shivering (TOS), and perceived cold were performed during all exposures. Shivering responses were evaluated by electromyography and visually. A significant (P<0.05), increase was seen in TOS (from 26.2 min to 55.6 min), and a significant decrease was seen in thermoregulatory heat production (from 14.78 kcal/h to –2.64 kcal/h) in group A; these changes were evident after about five exposures. It is concluded that the women became cold acclimated as a result of the repeated short-term resting cold air exposures.Research supported by Capes/Brazil, and by the Universidade Federal de Minas Gerais/Brazil     

Comparison of muscle force,muscle endurance,and electromyogram activity during an expedition at high altitude

Handgrip force (HF), maximal pinch force (MF), muscle endurance (ME), and the median power frequency (MdPF) of the activity shown in the electromyogram (EMG) were studied at various altitudes in eight normal healthy subjects. MF and ME were measured between the index finger and thumb, and all measurements were obtained at altitudes ranging from 610 to 4860 m during an expedition in the Qinghai Plateau in China. With the change in altitude HF, ME, and MF showed no significant change. Compared to the MdPF at 2260 m on ascent, the MdPF at other altitudes showed a significant decrease (P<0.01). Thus, we conclude that muscle performance (HF, MF, and ME) was not affected by the environment at high altitude. However, MdPF was affected and the mean MdPF at 610 m after the expedition did not recover to initial values of MdPF. We suggest these results may have been affected by fatigue and chronic exposure to the hypobaric hypoxic environment, since the members of the expedition party expressed feelings of sluggishness and fatigue after the expedition.     

Phospholipid composition and fatty acid desaturation in the roots of rye during acclimatization of low temperature

When the roots of rye plants grown at 20°C were cooled to 8°C the concentration of phospholipid in them more than doubled over a 7 d period in comparison with that in roots remaining at 20°C. The relative abundance of lecithin (PC) declined while that of phosphatidyl ethanolamine (PE) increased; this change was completed after 2 d cooling. Labelling with ³²P suggested that turnover of phospholipids may be inhibited by low temperature. Acyl lipids contained an increased proportion of linolenic acid (18:3) and reduced proportion of linoleic acid (18:2) when roots were cooled at 8°C for 7 d. The ratio of these acids is a relatively more sensitive indicator of desaturation than is the double bond index. Cooling brought about no change in the abundance of the principal saturated acid, palmitic (16:0). In the first 3 days of cooling PC and PE desaturated markedly while there was no change in galactosyl and neutral lipids. Desaturation did not appear to be greatly sensitive to the concentration of dissolved O₂ and was only partly inhibited in 8°C solutions where the oxygen concentration was lowered to 0.5–2.0%. Positional analysis of acyl chains in PC and PE showed that more than 90% of all 16:0 is associated with position I while 65% of the 18:2+18:3 is associated with position II. When roots are cooled the abundance of 18:3 increases in both chains but the relative distribution of saturated and unsaturated fatty acids remains constant in positions I and II. At both 20°C and 8°C there is a high probability that a saturated chain in position I will be paired with the polyunsaturated one in position II.Abbreviations PC Lecithin - PE phosphatidyl ethanolamine - TLC thin layerchromatography - BHT butylatedhydroxytoluene     

Highly efficient in vitro proliferation and genetic stability analysis of micropropagated Ceropegiaevansii by RAPD and ISSR markers: A critically endangered plant of Western Ghats

Ceropegiaevansii McCann (family: Asclepiadaceae), a critically endangered plant of Western Ghats has acquired significant importance due to its medicinal implications, edible tubers, and ornamental flowers. This study deals with the optimization of axillary bud proliferation using nodal explants followed by genetic stability analysis of regenerants. Maximum number of shoots (11.6 ± 1.1) was observed on the Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (4.0 mg/l) and indole-3-acetic acid (0.3 mg/l) with 85% shoot multiplication frequency. In vitro-grown shoots were rooted best in 1/2 MS medium supplemented with indole-3-butyric acid (1.0 mg/l) with an average of 10.3 ± 0.9 roots per shoot and 92% rooting frequency. Plantlets were acclimatized best (90%) in a mixture of sterile soil, sand, and coco peat (1:2:1). Micropropagated plants were subjected to random amplified polymorphic DNA and inter simple sequence repeat markers analyses. Collectively, 759 bands were generated which were monomorphic and similar to the mother plant. Findings of this study are the first report on micropropagation and assessment of genetic stability of micropropagated plantlets in C. evansii which suggests that axillary shoot proliferation can safely be used as an effective tool for propagation and conservation of C. evansii.     

Comparison of somatic embryogenesis-derived coffee (Coffea arabica L.) plantlets regenerated in vitro or ex vitro: morphological,mineral and water characteristics

Coffea arabica L. plantlets obtained ex vitro after sowing somatic embryos produced in a bioreactor in horticultural substrate were compared with those obtained in vitro from the same embryo population under conventional culturing conditions on semi-solid media. The intensity and quality of aerial and root system development were compared. Shoot emergence was more efficient in vitro but rooting frequencies were low. In contrast, all ex vitro-regenerated embryos rooted. The cotyledon area of mature embryos produced in a bioreactor positively affected plantlet development when regeneration was carried out ex vitro. Embryos with an intermediate cotyledon area (0.86 cm2) had the highest rates of plant conversion ex vitro (63%), and also resulted in vigorous plantlets. Mortality was higher in nursery conditions, but better plant development was obtained. The quality of plantlets produced under ex vitro conditions was reflected in better growth of the aerial and root systems, and also by similar morphological, mineral and water status characteristics to seedlings. Unlike roots formed on semi-solid media, those produced in soil were branched, fine (30-50% had a diameter of less than 0-5 mm) and they bore root hairs. Leaves of plantlets regenerated ex vitro had a histological structure similar to that of seedling leaves, and a lower stomatal density (100 vs. 233 mm-2). Moreover, they were more turgid, as indicated by higher pressure potential (psiP) (0.91 s. 0.30 MPa) and relative water content values (97 vs. 93%). Furthermore, under in vitro conditions, leaves had larger stomata which were abnormally round and raised. Direct sowing of germinated somatic embryos resulted in the rapid production of vigorous plantlets under ex vitro conditions, whilst removing the need for problematical and costly conventional acclimatization procedures.     

Seasonal environmental changes regulate the expression of the histone variant macroH2A in an eurythermal fish

Adaptation to cold and warm conditions requires dramatic change in gene expression. The acclimatization process of the common carp Cyprinus carpio L. in its natural habitat has been used to study how organisms respond to natural environmental changes. At the cellular level, adaptation to cold condition is accompanied by a dramatic alteration in nucleolar structure and a down regulation of the expression of ribosomal genes. We show that the enrichment of condensed chromatin in winter adapted cells is not correlated with an increase of the heterochromatin marker trimethyl and monomethyl K20H4. However, the expression of the tri methyl K4 H3 and of the variant histone macroH2A is significantly increased during the winter season together with a hypermethylation of CpG residues. Taking into account the properties of macroH2A toward chromatin structure and dynamics and its role in gene repression our data suggest that the increased expression of macroH2A and the hypermethylation of DNA which occurs upon winter-acclimatization plays a major role for the reorganization of chromatin structure and the regulation of gene expression during the physiological adaptation to a colder environment.     

In vitro propagation of the neotropical giant bamboo, Guadua angustifolia Kunth, through axillary shoot proliferation

Guadua angustifolia Kunth was successfully propagated in vitro from axillary buds. Culture initiation, bud sprouting, shoot and plant multiplication, rooting and acclimatization, were evaluated. Best results were obtained using explants from greenhouse-cultivated plants, following a disinfection procedure that comprised the sequential use of an alkaline detergent, a mixture of the fungicide Benomyl and the bactericide Agri-mycin, followed by immersion in sodium hypochlorite (1.5% w/v) for 10 min, and culturing on Murashige and Skoog medium containing 2 ml l^?1 of Plant Preservative Mixture^®. Highest bud sprouting in original explants was observed when 3 mg l^?1 N⁶-benzylaminopurine (BAP) was incorporated into the culture medium. Production of lateral shoots in in vitro growing plants increased with BAP concentration in culture medium, up to 5 mg l^?1, the highest concentration assessed. After six subcultures, clumps of 8–12 axes were obtained, and their division in groups of 3–5 axes allowed multiplication of the plants. Rooting occurred in vitro spontaneously in 100% of the explants that produced lateral shoots. Successful acclimatization of well-rooted clumps of 5–6 axes was achieved in the greenhouse under mist watering in a mixture of soil, sand and rice hulls (1:1:1).     

In vitro propagation of three <Emphasis Type="Italic">Agave</Emphasis> species used for liquor distillation and three for landscape

In vitro bud clusters of Calathea orbifolia (Linden) Kennedy were obtained and subcultured in semi-solid (agar) medium and temporary immersion system (TIS) for 12 weeks. Uniform young plants were selected and transferred to soilless mix in a growth chamber for ex vitro acclimatization during 35 days, followed by growing in a shaded greenhouse for 65 days. Comparison of in vitro leaf anatomy, ex vitro photosynthetic behaviors and growth was made between two cultural systems. Plants in TIS produced thicker leaf chlorenchyma and aquiferous parenchyma, lower stomatal frequency and more epicuticular wax than did those in semi-solid medium. Plants from semi-solid medium had consistently lower leaf Fv/Fm values than plants from TIS. Leaf Fv/Fm value in plants from TIS decreased to 0.65 at day 7 after transfer and increased soon up to 0.76 thereafter. In contrast, leaf Fv/Fm value in plants from semi-solid medium reduced to 0.27 at day 7 after transfer and increased slowly up to 0.68 at day 35. During ex vitro acclimatization, plants in TIS had substantial higher photosynthetic rates than plants in semi-solid medium. Plants from TIS had subsequent higher leaf area, fresh and dry weights than plants from semi-solid medium.     

Effect of plant growth regulators on indirect shoot organogenesis of Ficus religiosa through seedling derived petiole segments

Ficus religiosa is known as a long-lived multipurpose forest tree. The tree plays an important role for religious, medicinal, and ornamental purposes. However, the propagation rate of Ficus religiosa is low in natural habitat so the plant tissue culture techniques are an applicable method for multiplication of this valuable medicinal plants. Thus, the aim of this study is to understand the effect of different auxin/cytokinin ratios on indirect shoot organogenesis of this plant. According to our results, the maximum callus induction frequency (100%) was obtained on Murashige and Skoog (MS) medium supplemented with 0.5?mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) plus 0.05?mg/l 6-benzylaminopurine (BAP) from petiole segments. For shoot induction purpose, the yellow-brownish, friable, organogenic calli were inoculated on shoot induction medium. On MS medium supplemented with 1.5?mg/l BAP and 0.15?mg/l Indole-3-butyric acid (IBA), 96.66% of the petiole-derived calli responded with an average number of 3.56 shoots per culture. The highest root formation frequency (96.66%), root number (5.5), and root length (4.83?cm) were achieved on MS medium containing 2.0?mg/l IBA plus 0.1?mg/l Naphthaleneacetic acid (NAA). The rooted shoots were successfully transferred to field condition and the substrate with the mixture of cocopeat and perlite (1:1) had the highest survival rate (96.66%). This is the first report of an effective in vitro organogenesis protocol for F. religiosa by indirect shoot organogenesis through axenic seedling derived petiole explants, which can be efficiently employed for conservation of this important medicinal plant species as well as the utilization of active biomolecules.     

Effect of arbuscular mycorrhizal fungi on the acclimatization of micropropagated banana plantlets

 The effect of arbuscular mycorrhizal fungi (AMF) on micropropagated banana plantlets was evaluated during the acclimatization period. Plants were inoculated with Acaulospora scrobiculata, Glomus clarum or Glomus etunicatum. After cultivation in a greenhouse for 3 months, height, leaf area, fresh weight and dry matter of root and shoots, level of AMF colonization, nutrient level, photosynthesis and transpiration rate, water potential and stomatal conductance were measured. The number of AMF spores produced in each treatment was also determined. Plantlets inoculated with AMF had greater height, leaf area and fresh weight of shoots and roots, as well as higher rates of photosynthesis and transpiration than controls. Plants inoculated with Glomus were superior in most of the evaluated parameters. Accepted: 24 May 1999