Purification and characterisation of a jacalin-related, coleoptile specific lectin from Hordeum vulgare

A plant lectin was isolated from barley (Hordeum vulgare) coleoptiles using acidic extraction and different chromatographic methods. Sequencing of more than 50% of the protein sequence by Edman degradation confirmed a full-length cDNA clone. The subsequently identified open reading frame encodes for a 15 kDa protein which could be found in the soluble fraction of barley coleoptiles. This protein exhibited specificity towards mannose sugar and is therefore, accordingly named as Horcolin (Hordeum vulgare coleoptile lectin). Database searches performed with the Horcolin protein sequence revealed a sequence and structure homology to the lectin family of jacalin-related lectins. Together with its affinity towards mannose, Horcolin is now identified as a new member of the mannose specific subgroup of jacalin-related lectins in monocot species. Horcolin shares a high amino acid homology to the highly light-inducible protein HL#2 and, in addition to two methyl jasmonic acid-inducible proteins of 32.6 and 32.7 kDa where the jasmonic acid-inducible proteins are examples of bitopic chimerolectins containing a dirigent and jacalin-related domain. Immunoblot analysis with a cross-reactive anti-HL#2 antibody in combination with Northern blot analysis of the Horcolin cDNA revealed tissue specific expression of Horcolin in the coleoptiles. The function of Horcolin is discussed in the context of its particular expression in coleoptiles and is then compared to other lectins, which apparently share a related response to biotic or abiotic stress factors.     

5. SOME NOTES RESULTING FROM A HOLIDAY TRIP THROUGH EAST GRIQUALAND

The study investigated the bird species diversity associated with vegetation communities found on a single mountain slope in the Usuthu Gorge Community Conservation Area, northern KwaZulu-Natal. Thirteen sample sites were surveyed on a monthly basis for 12 months. Over this period, 279 birds and 55 species were recorded, of which the Dark-capped Bulbul Pycnonotus tricolor was the most abundant. The Rattling Cisticola Cisticola chiniana was the indicator species in the highest community, Open Bushveld, which is characterised by grassland and bush patches. The White-bellied Sunbird Cinnyris talatala was an indicator in the second-lowest community, Dense Bushveld–Woodland, which is characterised by steep slopes and thickets. In Wooded Grassland, located between the above two communities, the highest beta diversity (species turnover) was recorded and this outcome was probably caused by large areas covered by rocks that compelled woodland birds to move through this community. Contrary to expectation, the gamma diversity per vegetation community increased with elevation from 18 to 33 species in Dense Bushveld–Woodland, Wooded Grassland and Open Bushveld. A future study should measure bird species diversity on larger elevational gradients, i.e. slopes from 500 to 3 000 m above sea level, which also include more distinct vegetation communities.     

Plasma lactate, GH and GH-binding protein levels in exercise following BCAA supplementation in athletes

Summary. Branched chain amino acids (BCAA) stimulate protein synthesis, and growth hormone (GH) is a mediator in this process. A pre-exercise BCAA ingestion increases muscle BCAA uptake and use. Therefore after one month of chronic BCAA treatment (0.2 g kg⁻¹ of body weight), the effects of a pre-exercise oral supplementation of BCAA (9.64 g) on the plasma lactate (La) were examined in triathletes, before and after 60 min of physical exercise (75% of VO₂max). The plasma levels of GH (pGH) and of growth hormone binding protein (pGHBP) were also studied. The end-exercise La of each athlete was higher than basal. Furthermore, after the chronic BCAA treatment, these end-exercise levels were lower than before this treatment (8.6 ± 0.8 mmol L⁻¹ after vs 12.8 ± 1.0 mmol L⁻¹ before treatment; p < 0.05 [mean ± std. err.]). The end-exercise pGH of each athlete was higher than basal (p < 0.05). Furthermore, after the chronic treatment, this end-exercise pGH was higher (but not significantly, p = 0.08) than before this treatment (12.2 ± 2.0 ng mL⁻¹ before vs 33.8 ± 13.6 ng mL⁻¹ after treatment). The end-exercise pGHBP was higher than basal (p < 0.05); and after the BCAA chronic treatment, this end-exercise pGHBP was 738 ± 85 pmol L⁻¹ before vs 1691 ± 555 pmol L⁻¹ after. pGH/pGHBP ratio was unchanged in each athlete and between the groups, but a tendency to increase was observed at end-exercise. The lower La at the end of an intense muscular exercise may reflect an improvement of BCAA use, due to the BCAA chronic treatment. The chronic BCAA effects on pGH and pGHBP might suggest an improvement of muscle activity through protein synthesis. Received January 5, 1999 / Accepted June 17, 1999     

Determination of metabolic equivalents during low- and high-intensity resistance exercise in healthy young subjects and patients with type 2 diabetes

The purpose of this study was to quantify the metabolic equivalents (METs) of resistance exercise in obese patients with type 2 diabetes (T2DM) and healthy young subjects and to evaluate whether there were differences between sessions executed at low- versus high-intensity resistance exercise. Twenty obese patients with T2DM (62.9±6.1 years) and 22 young subjects (22.6±1.9 years) performed two training sessions: one at vigorous intensity (80% of 1-repetition maximum (1RM)) and one at moderate intensity (60% of 1RM). Both groups carried out three strength exercises with a 2-day recovery between sessions. Oxygen consumption was continuously measured 15 min before, during and after each training session. Obese T2DM patients showed lower METs values compared with young healthy participants at the baseline phase (F= 2043.86; P<0.01), during training (F=1140.59; P<0.01) and in the post-exercise phase (F=1012.71; P<0.01). No effects were detected in the group x intensity analysis of covariance. In this study, at both light-moderate and vigorous resistance exercise intensities, the METs value that best represented both sessions was 3 METs for the obese elderly T2DM patients and 5 METs for young subjects.     

Cardiovascular responses to sustained maximal isometric contractions of the finger flexors

This study investigated cardiovascular responses to 2 min sustained submaximal (20% MVC) and maximal (100% MVC) voluntary isometric contractions of the finger flexors in healthy young women. Cardiovascular variables investigated were: heart rate (f _c), mean arterial pressure ( _a), and stroke volume (SV). Doppler echocardiography was used to estimate SV from measures of aortic diameter (AD) and time-velocity integrals. Preliminary studies indicated that AD did not change significantly after 2 min sustained 100% MVC. Therefore, pre-exercise AD values were used to calculate SV before, during and after exercise. During the 2-min 100% MVC period, f _c and _aincreased significantly during the first 30 s of contraction. f _c then remained constant during the remainder of the 2-min contraction period, while _acontinued to rise. SV did not change significantly during the 100% MVC task but increased significantly during recovery from sustained 100% MVC. The data suggest that the magnitude of cardiovascular responses to isometric exercise is dependent on the specific task performed, and that there is a different pattern of response for f _c, _a, and SV during 20% and 100% MVC tasks. Unlike f _c and _a, SV did not change significantly during isometric exercise, but increased significantly after sustained 100% MVC.