Effect of heat stress on muscle blood flow during dynamic handgrip exercise

During exercise in a hot environment, blood flow in the exercising muscles may be reduced in favour of the cutaneous circulation. The aim of our study was to examine whether an acute heat exposure (65-70 degrees C) in sauna conditions reduces the blood flow in forearm muscles during handgrip exercise in comparison to tests at thermoneutrality (25 degrees C). Nine healthy men performed dynamic handgrip exercise of the right hand by rhythmically squeezing a water-filled rubber tube at 13% (light), and at 34% (moderate) of maximal voluntary contraction. The left arm served as a control. The muscle blood flow was estimated as the difference in plethysmographic blood flow between the exercising and the control forearm. Skin blood flow was estimated by laser Doppler flowmetry in both forearms. Oesophageal temperature averaged 36.92 (SEM 0.08) degrees C at thermoneutrality, and 37.74 (SEM 0.07) degrees C (P less than 0.01) at the end of the heat stress. The corresponding values for heart rate were 58 (SEM 2) and 99 (SEM 5) beats.min-1 (P less than 0.01), respectively. At 25 degrees C, handgrip exercise increased blood flow in the exercising forearm above the control forearm by 6.0 (SEM 0.8) ml.100 ml-1.min-1 during light exercise, and by 17.9 (SEM 2.5) ml.100 ml-1.min-1 during moderate exercise. In the heat, the increases were significantly higher: 12.5 (SEM 2.2) ml.100 ml-1.min-1 at the light exercise level (P less than 0.01), and 32.2 (SEM 5.9) ml.100 ml-1.min-1 (P less than 0.05) at the moderate exercise level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Response of Whole Blood,Erythrocyte and Plasma Vitamin E Content to Dietary Vitamin E Intake in the Chick

Whole blood, red blood cells (RBC), and plasma vitamin E (VE) levels in chicks fed dietary VE (dl-α-tocopheryl acetate, dl-αTa) supplementation in steps of 0.0, 5.0, 10.0, 15.0, 20.0 and 30.0 mg/Kg were determined to examine their usefulness as an index of VE status. The increase in VE level was significant and linear in whole blood (r = 0.90), RBC (r = 0.89) and plasma (r = 0.93) in response to dietary VE intake. There was a close correlation between VE in plasma vs whole blood (r = 0.90), plasma vs RBC (r = 0.91) and whole blood vs RBC (r = 0.95). The plasma VE content was 1.2–1.8 times greater than that of whole blood, and 6.6–12.5 times greater than that of RBC. The plasma total lipids content was not affected by the dietary VE intake, whereas the level of VE in the plasma total lipids was significantly increased with increasing supplementation. Alpha tocopherol was the major isomer (ca 92 %) of VE in whole blood, RBC and plasma at hatching. The small proportions of β-tocopherol (ca 2 %), γ-tocopherol (ca 5 %) and α-tocotrienol (ca 1 %) observed at 1 day of age had decreased or totally disappeared by 7 days of age after feeding the VE-free basal diet. The data showed that in the chick, the whole blood and RBC levels of VE were as sensitive and reliable indexes of dietary VE status as was that of the plasma.     

Bovine αs1-casein gene sequences direct high level expression of human granulocyte-macrophage colony-stimulating factor in the milk of transgenic mice

The generation is reported of transgenic mice expressing human granulocyte-macrophage colony-stimulating factor (GM-CSF) or human erythropoietin (EPO) under the control of bovine s1- casein regulatory sequences. GM-CSF expression was specific to the mammary gland, and levels of human GM-CSF in transgenic mouse milk were in the range of mg ml–1. The specific activity of the milk GM-CSF was similar to that of the recombinant protein produced in Escherichia coli, and the glycosylation-derived size heterogeneity corresponded to that of the native human protein. In spite of the identical bovine regulatory sequences of the fusion genes, the levels of human EPO in transgenic mouse milk were 103--106 times lower than those of GM-CSF, ranging from 0.003 to 3 g ml–1. There appeared to be a positive correlation between the amount of EPO in the milk of lactating females and blood haematocrit values. In view of this, other type of constructs should be used to achieve more efficient EPO expression and to circumvent concomitantly-occurring adverse effects. In contrast, the high-level production of recombinant GM-CSF, its resemblance to the native mammalian protein, and mild adverse consequences of transgene expression imply that the current construct could be used for generation of larger GM-CSF transgenic anim als to produce this protein in quantities sufficient for therapeutic purposes     

Alcohol detoxification accelerated by oxygenated drinking water.

The liver eliminates ethanol through several oxygen dependent processes. Since the liver receives most of its blood flow through the portal vein, it should be possible to increase its oxygen tension by augmenting the oxygen saturation of the portal vein. We therefore studied elimination of ethanol administered intravenously to three monkeys who received strongly oxygenated drinks at 20 to 30 minute intervals during the whole experiment. From these drinks dissolved oxygen was presumably released in the stomach and upper intestine and arrived to the liver along the portal vein. As a consequence of this treatment the elimination rate of ethanol increased 60 % on the average. The increase was significant on the level of p < 0.02. The production of acetaldehyde also increased but less significantly. Measurements of oxygen tensions in the portal blood of two anaesthetized dogs indicated 7 and 8 % increases lasting for 10 and 15 minutes after infusion of oxygenated water into the stomach.     

Hydrolysis of ester substrates of trypsin and chymotrypsin by barley carboxypeptidase

Purified barley carboxypeptidase exhibits high activity against a number of N-substituted amino acid esters, which are commonly used as synthetic substrates for mammalian and microbial proteinases. The proteinases of barley, on the contrary, do not hydrolyse these compounds. Because many other plants contain carboxypeptidases closely resembling the barley enzyme, we conclude that synthetic ester substrates should not be used to detect proteinase activity in extracts of higher plants. Plant carboxypeptidases also liberate C-terminal tryptophan from α-casein. Therefore, casein also is an unreliable substrate for plant proteinases.     

Effects of colchicine and vinblastine on neurotubules of the sciatic nerve and cholinesterases in the developing myoneural junction of the rat

Summary Colchicine (0.1 M) or vinblastine (0.01 M) was locally applied on the sciatic nerves of newborn rats. Both colchicine and vinblastine caused reversible disappearance of axonal neurotubules and appearance of increased amounts of neurofilaments at the site of application. Subsequent morphogenesis of myoneural junctions in the tibialis anterior muscle was studied after histochemical demonstration of acetylcholinesterase (AChE; E.C. 3.1.1.7) and non-specific cholinesterase (Ns. ChE; E.C. 3.1.1.8) activity in the myoneural area.Development of the postsynaptic muscle plasma membrane of the myoneural junction was arrested in the ipsilateral, but not in the contralateral control side, for a period of about three weeks following treatment with the test substances. After this delay the myoneural morphogenesis continued normally and neurotubules were seen in the axoplasm.Since disruption of neurotubules is likely to cause blockage of the intratubular axoplasmic transport system, it seems possible that the neurotrophic influence responsible for the development of the postsynaptic muscle membrane is mediated through a secretory product transported along axons intratubularly to the nerve endings.     

Distribution of aquaporin 4 on sarcolemma of fast-twitch skeletal myofibres

The aquaporin 4 (AQP4) water channel is present on the sarcolemma of fast-twitch-type skeletal myofibres. We have examined the distribution of AQP4 in relation to sarcolemmal domain structure and found that AQP4 protein is not evenly distributed on the sarcolemma. Immunofluorescence staining of isolated single myofibres indicated a punctate staining pattern overlapping with the dystrophin glycoprotein complex, but with the transverse tubule openings being left clear. Myotendinous and neuromuscular junctions also lacked AQP4, despite their high content of the dystrophin glycoprotein complex. The destruction of caveoli with methyl-β-cyclodextrin did not change the distribution of AQP4 at the sarcolemma. Moreover, AQP4 did not float with the caveolar marker caveolin-3 in sucrose gradients after Triton X-100 extraction at 4°C. These data indicated that AQP4 was not associated with caveoli. Surprisingly, m. flexor digitorum brevis fibres, although of the fast-twitch type, often lacked AQP4. Furthermore, those fibres harbouring AQP4 at the sarcolemma showed a regionalized distribution, suggesting that large areas were devoid of the protein. Blockage of the synthesized proteins in the endoplasmic reticulum with brefeldin A showed that, in spite of its regionalized sarcolemmal distribution, AQP4 was synthesized along the entire length of the fibres. These results suggest functional differences in the water permeability of the sarcolemma not only between the fast-twitch muscles, but also within single muscle fibres.     

Student-generated instructional videos facilitate learning through positive emotions

The central focus of this study is a learning method in which university students produce instructional videos about the content matter as part of their learning process, combined with other learning assignments. The rationale for this is to promote a more multimodal pedagogy, and to provide students opportunities for a more learner-centred, motivating, active, engaging and productive role in their learning process. As such we designed a ‘video course’ where the students needed to produce an instructional video which could be used for university teaching. In addition to producing the video, the students needed to write a literature review of the topic of the video and a learning journal. At the end of the course the students filled a questionnaire regarding their learning and emotions during the project. Based on the students’ subjective answers, it appeared that producing a video, combined with writing the literature review can be an efficient way of learning. Most students found the project emotionally very positive and regarded it motivating to work on a video which they knew will have use in the future. This research suggests that a multimodal video project in a higher education setting enhances learning through increased motivation and positive emotions.     

Exopolysaccharide-Producing Bacteria from Sugar Beets

Six hundred microorganisms were isolated from sugar beets collected from different parts of Finland to study their slime production. A total of 170 of them produced exopolysaccharides, of which 35% were heteropolysaccharides. The yield of heteropolysaccharides from sucrose was lower than that of dextrans. Five isolates, which were chosen for closer study, were identified as Leuconostoc mesenteroides (two species), Rahnella aquatilis (two species), and Enterobacter amnigenus.