Genetic Diversity of the Wild Banana Musa acuminata Colla in Malaysia as Evidenced by AFLP

Musa acuminata Colla (Musaceae), the wild progenitor of thecultivated banana, is highly variable in Malaysia and presentsseveral unresolved nomenclatural problems. AFLP was employedto distinguish among three subspecies of Musa acuminata(subsp.truncata and subsp. malaccensis from peninsular Malaysia andsubsp. microcarpa from Borneo) and to examine whether subsp.truncata is a distinct taxon. Eight primer combinations revealedmolecular markers specific for each of the three taxa. UPGMAcluster analysis showed the three taxa were distinct. Subspeciesmalaccensis which is endemic in peninsular Malaysia and subsp.microcarpa which is endemic in Borneo were found to be moresimilar to each other in their DNA patterns than they are tosubsp. truncata, which is endemic to peninsular Malaysia. Sincesubsp. truncata is genetically separate from subsp. malaccensisand subsp.microcarpa , it cannot be regarded as synonymous witheither of these subspecies. This paper sheds light on the nomenclatureof the three subspecies of Musa acuminata. Copyright 2001 Annalsof Botany Company Musa acuminata Colla, truncata, malaccensis, microcarpa, Musaceae, wild banana, genetic diversity, AFLP, DNA fingerprinting     

Small bowel tonometry is more accurate than gastric tonometry in detecting gut ischemia

Gastric tonometerPCO₂ measurement may help identifygut ischemia in critically ill patients but is frequentlyassociated with large measurement errors. We tested the hypothesis thatsmall bowel tonometer PCO₂measurement yields more accurate information. In 10 anesthetized,mechanically ventilated pigs subject to progressive hemorrhage, wemeasured gut oxygen delivery and consumption. We also measuredtonometer PCO₂ minus arterialPCO₂(PCO₂) and calculated the corresponding intracellular pH from tonometers placed in the stomach and jejunum. We found that the correlation coefficient(r²) forbiphasic gut oxygen delivery-PCO₂relationships was 0.29 ± 0.52 for the gastric tonometer vs. 0.76 ± 0.25 for the small bowel tonometer(P < 0.05). In addition, thecritical gastric tonometer PCO₂was excessively high and variable (62.9 ± 39.6) compared with thecritical small bowel tonometerPCO₂ (17.0 ± 15.0, P < 0.01). Small bowel tonometerPCO₂ was closely correlated withsuperior mesenteric vein PCO₂(r² = 0.81, P < 0.001), whereas gastrictonometer PCO₂ was not(r² = 0.13, P = not significant). Weconclude that measurement of gastric tonometerPCO₂ yields excessively noisy andinaccurate data on the onset of gut anaerobic metabolism in hemorrhagicshock. Small bowel tonometer PCO₂ isless noisy and, as a result, is superior in detecting gut hypoperfusionand the onset of anaerobic metabolism.

     

Studies on Gracilaria changii (Gracilariales,Rhodophyta) from Malaysian mangroves

Gracilaria changii, recorded from Malaysia and Thailand, is one of the more abundant agarophytic seaweeds found in Malaysia. A wild population of Gracilaria changii growing in mangroves was monitored for seasonal variation in agar content and gel strength as well as spore production. Agar yield and gel strength ranged from 12 to 25% dry weight and 294 to 563 g cm^–2, respectively, over a 15-month period. Gel strength but not yield was positively correlated with amount of rainfall. Cystocarps were observed throughout the study, but use of sporetraps showed that spore release peaked around July–August and January–February after the two monsoon periods.Mariculture of Gracilaria changii in shallow ponds in the mangroves, in an irrrigation canal and in a shrimp farm pond was conducted. Average growth rate of cuttings tied to monofilament lines was 3.3 ± 1.7% d^–1, 8.4 ± 1.8% d^–1 and 3.6 ± 1.6% d^–1 respectively. Cuttings were lost to siltation, wave action, predation and heavy epiphytisation.These studies show that Gracilaria changii has potential commercial application in the agar industry.     

Proline biosynthesis: multiple defects in Chinese hamster ovary cells

The biochemical basis for the proline requirement of Chinese hamster ovary cells has been investigated. The results indicate an absence of conversion of glutamate to proline and a 90% reduction in ornithine transaminase, the first enzyme in the pathway converting ornithine to proline. Possible explanations for this double defect are discussed.     

Cys32 and His105 are the critical residues for the calcium-dependent cysteine proteolytic activity of CvaB, an ATP-binding cassette transporter

CvaB, a member of the ATP-binding cassette transporter superfamily, is the central membrane transporter of the colicin V secretion system in Escherichia coli. Cys32 and His105 in the N-terminal domain of CvaB were identified as critical residues for both colicin V secretion and cysteine proteolytic activity. By inhibiting degradation with N-ethylmaleimide and a mixture of protease inhibitors, a stable wild-type N-terminal domain (which showed cysteine protease activity when activated) was purified. Such protease activity was Ca2+- and concentration-dependent and could be inhibited by antipain, N-ethylmaleimide, EDTA, and EGTA. At low concentrations, the Ca2+ analogs Tb3+ and La3+ (but not Fe3+) significantly enhanced proteolytic activity, suggesting that the size of the cations is important for activity. Together with comparisons of the sequences of members of the cysteine protease family, these results indicate that Cys32 and His105 are the critical residues in the CvaB N-terminal domain for the calcium-dependent cysteine protease activity and secretion of colicin V.     

Proline synthesis and redox regulation: Differential functions of pyrroline-5-carboxylate reductase in human lymphoblastoid cell lines

Pyrroline-5-carboxylate (P5C) reductase not only catalyzes the final step in proline biosynthesis but also mediates redox regulation. We examined these dual functions in human lymphoblastoid cell lines (REH, LHN₁₃) one of which (REH) is deficient in proline synthesis. In spite of the deficiency in proline synthesis in REH, the PC-mediated redox effect was relatively intact. The dissociation of these functions was due to qualitative as well as quantitative differences in the REH enzyme relative to its utilization of NADPH and NADH.     

Kappaphycus malesianus sp. nov.: a new species of Kappaphycus (Gigartinales,Rhodophyta) from Southeast Asia

A new species, Kappaphycus malesianus, is established as a new member of the genus Kappaphycus. Locally known as the “Aring-aring” variety by farmers in Malaysia and the Philippines, this variety has been commercially cultivated, often together with Kappaphycus alvarezii due to the similarities in morphology. Despite also producing kappa-carrageenan, the lower biomass of the K. malesianus when mixed with K. alvarezii ultimately affects the carrageenan yield. Morphological observations, on both wild and cultivated plants, coupled with molecular data have shown K. malesianus to be genetically distinct from its Kappaphycus congeners. The present study describes the morphology and anatomy of this new species as supported by DNA data, with additional morphological features for distinguishing between commercial Kappaphycus cultivars.