Oxygen uptake capacity of gills and skin in relation to body weight of the air-breathing siluroid fish, Clarias batrachus (Linn.).

Oxygen consumption through gills and skin in relation to body weight was estimated in the air-breathing catfish, Clarias batrachus, under two experimental conditions, viz., (i) when access to air was allowed and (ii) when air-breathing was prevented. There was a positive correlation between VO2 (ml/hr) and body weight in both experimental conditions. Oxygen consumption (ml/hr) increased by a power of 0.869 when access to air was allowed whereas the power was slightly less (b = 0.841) when air-breathing was prevented. As the values for exponent (b) were less than 1.0, the weight specific VO2 (ml/kg/hr) decreased with increasing body weight. The decrease was more marked (b = - 0.180) in fishes which were not allowed air than in those where access to air was allowed (b = - 0.148). Under normal conditions of water and air-breathing the rate of VO2 (ml/kg/hr) via gills and skin from water ranged from 39.7 +/- 3.21 to 76.7 +/- 9.01 and this increased to 42.17 +/- 6.2 to 105.9 +/- 8.33 when air-breathing was prevented. The increase in the rate of VO2 was perhaps associated with the increase in the volume of water irrigating the gills per unit time.     

Gene expression in allergenic pollen

The molecular mechanism of gene expression for pollen specificity is not yet fully known. However, it is an exciting area with great potential and has a wide scope of application in the field of molecular biology, breeding systems, biotechnology etc. The main aim of this write-up is to review some of the interesting achievements made through studies like gene expression in allergic pollen and the research which will make a way towards practical application of pollen molecular biology in identifying and isolating the genes responsible for all allergic disorders reported among various individuals. This revised version was published online in June 2006 with corrections to the Cover Date.     

Lipid biosynthesis in seeds of mustard (Brassica juncea) influenced by zinc and sulphur deficiency

In developing seeds of mustard ( Brassica juncea L. cv. RLM 198) the period between 20 and 30 days after fertilization (DAF) was identified as the period of active lipid biosynthesis, although dry matter continued to accumulate until maturity. The period of lipid synthesis was associated with a decrease in starch, soluble sugars and protein, thus, giving rise to precursors for the biosynthesis of lipids. Besides decreasing the dry matter content (on both % and seed basis), Zn and S deficiency caused a significant ( P > 0.05) reduction in oil content. As compared to control, the decrease in oil content was 11, 12 and 18% at 30 DAF and 4, 9 and 16% at maturity in Zn, S and (Zn+S) deficient treatments, respectively. Throughout the period of seed development, a significant decrease in starch and protein with a slight accumulation of soluble sugars was observed due to deficiency of Zn or S. The rate of [l-¹⁴C]-acetate incorporation into total lipids, which was maximal at 30 DAF, also displayed a significant decrease due to the abovementioned mineral deficiencies. Addition of Zn or S in vitro, enhanced the lipid synthesis at all stages of seed development. Under Zn and S deficiency, the phospholipids increased from 10 to 30 DAF and then declined until maturity. However, the proportion of glycolipids and free fatty acids increased, with a corresponding decrease in total glycerides. Further, in deficiency treatments, there was an increase in 22:1 with a corresponding decrease in 18:1, 18:2 and 18:3 in developing and mature mustard seeds.     

Replication of Nuclei from Cycling and Quiescent Mammalian Cells in 6-DMAP-TreatedXenopusEgg Extract

Nuclear membrane permeabilization is required for replication of quiescent (G0) cell nuclei inXenopusegg extract. We now demonstrate that establishment of replication competence in G0 nuclei is dependent upon a positive activity present in the soluble egg extract. Our hypothesis is that G0 nuclei lose the license to replicate following growth arrest and that this positive activity is required for relicensing DNA for replication. To determine if G0 nuclei contain licensed DNA, we used the protein kinase inhibitor, 6-dimethylaminopurine (6-DMAP), to prepare egg extracts that are devoid of licensing activity. Intact nuclei, isolated from mammalian cells synchronized in G1-phase (licensed), G2-phase (unlicensed), and G0 were permeabilized and assayed for replication in 6-DMAP-treated and untreated extracts supplemented with [α-³²P]dATP or biotinylated-dUTP. Very little radioactivity was incorporated into nascent DNA in each nuclear population; however, nearly all nuclei in each population incorporated biotin in 6-DMAP extract. The pattern of biotin incorporation within these nuclei was strikingly similar to the punctate pattern observed within nuclei incubated in aphidicolin-treated extract, suggesting that initiation events occur within most replication factories in 6-DMAP extract. However, density substitution and alkaline gel analyses indicate that the incorporated biotin within these nuclei arises from a small number of active origins which escape 6-DMAP inhibition. We conclude that 6-DMAP-treated egg extract cannot differentiate licensed from unlicensed mammalian somatic cell nuclei and, therefore, cannot be used to determine the “licensed state” of G0 nuclei using the assays described here.     

Reliability of the calculated maximal lactate steady state in amateur cyclists

Complex performance diagnostics in sports medicine should contain maximal aerobic and maximal anaerobic performance. The requirements on appropriate stress protocols are high. To validate a test protocol quality criteria like objectivity and reliability are necessary. Therefore, the present study was performed in intention to analyze the reliability of maximal lactate production rate (V.L_amax) by using a sprint test, maximum oxygen consumption (V.O_2max) by using a ramp test and, based on these data, resulting power in calculated maximum lactate-steady-state (PMLSS) especially for amateur cyclists. All subjects (n = 23, age 26 ± 4 years) were leisure cyclists. At three different days they completed first a sprint test to approximate V.La_max. After 60 min of recreation time a ramp test to assess V.O_2max was performed. The results of V.La_max-test and V.O_2max-test and the body weight were used to calculate PMLSS for all subjects. The intra class correlation (ICC) for V.La_max and V.O_2max was 0.904 and 0.987, respectively, coefficient of variation (CV) was 6.3% and 2.1%, respectively. Between the measurements the reliable change index of 0.11 mmol·l ^-1s ^-1 for V.La_max and 3.3 mlkg ^-1min ^-1 for V.O_2max achieved significance. The mean of the calculated PMLSS was 237 ± 72 W with an RCI of 9 W and reached with ICC = 0.985 a very high reliability. Both metabolic performance tests and the calculated PMLSS are reliable for leisure cyclists.     

Key features of the two-intron Saccharomyces cerevisiae gene SUS1 contribute to its alternative splicing

Alternative pre-mRNA splicing allows dramatic expansion of the eukaryotic proteome and facilitates cellular response to changes in environmental conditions. The Saccharomyces cerevisiae gene SUS1, which encodes a protein involved in mRNA export and histone H2B deubiquitination, contains two introns; non-canonical sequences in the first intron contribute to its retention, a common form of alternative splicing in plants and fungi. Here we show that the pattern of SUS1 splicing changes in response to environmental change such as temperature elevation, and the retained intron product is subject to nonsense-mediated decay. The activities of different splicing factors determine the pattern of SUS1 splicing, including intron retention and exon skipping. Unexpectedly, removal of the 3' intron is affected by splicing of the upstream intron, suggesting that cross-exon interactions influence intron removal. Production of different SUS1 isoforms is important for cellular function, as we find that the temperature sensitivity and histone H2B deubiquitination defects observed in sus1Δ cells are only partially suppressed by SUS1 cDNA, but SUS1 that is able to undergo splicing complements these phenotypes. These data illustrate a role for S. cerevisiae alternative splicing in histone modification and cellular function and reveal important mechanisms for splicing of yeast genes containing multiple introns.