A PvuII polymorphism near exon 2 of the dystrophin gene

We report a PvuII polymorphism near exon 2 of the dystrophin gene with a heterozygosity frequency of 0.5.     

Cloning and analysis of the polyhydroxyalkanoic acid synthase gene from an Acinetobacter sp.: Evidence that the gene is both plasmid and chromosomally located

Abstract The polyhydroxyalkanoic acid (PHA) synthase gene ( phaC_Ac ) of a species of Acinetobacter isolated from an activated sludge treatment plant was cloned by heterologous complementation in a poly-β-hydroxybutyrate (PHB) negative mutant of Alcaligenes eutrophus . Nucleotide sequence analysis of phaC_Ac revelaed an open reading frame of 1770 bp with potential to encode a 67.7 kDa protein. The deduced amino acid sequence displays high similarity to other PHA synthase proteins. Probing with an internal region of phaC_Ac revealed that the PHA sythase gene may be present in more than one copy and may occur at both plasmid and chromosomal locations in Acinetobacter spp. This is the first organisms for which evidence has been presented to suggest that a gene involved in PHA metabolism is plasmid-encoded. Purification of PHB granules from sucrose gradients identified proteins of 38 kDa, 41 kDa and 64 kDa which may have a role in PHB metabolism.     

Dry-season spawning in a cyprinid fish of southern India

Synopsis A population of the S. Indian cyprinid fishBarbus melanampyx was sampled monthly through 24 months. Seasonal cycles of the gonado-somatic index (GSI), ovarian stages, male breeding tubercles, spawning behaviour and population structure were assessed. These fish breed strictly seasonally during the main dry period: December/January through April. Comparison with other Barbus species of the same general region led to the conclusion that the patterns of reproductive investment ofB. melanampyx are similar to those of perennial species, and different from those of wet-season spawners. The reasons for this rather unexpected result were found in the more constant conditions prevailing during a dry season as compared to the monsoon. It was argued thatB. melanampyx and the species spawning perennially are in effect small-brood spawners, rather than partial spawners.     

A review of hybridization in marine angelfishes (Perciformes: Pomacanthidae)

Synopsis Although hybridization of terrestrial and freshwater organisms has been well-studied, very little work has focused on hybridization among coral reef fish species. In the present paper, eleven examples of probable hybrids between marine angelfishes (Pomacanthidae) are reviewed. Evidence is presented which strongly suggests that the nominal speciesApolemichthys armitagei is invalid and that specimens previously identified as this species represent hybrids betweenA. trimaculatus andA. xanthurus. Of the remaining ten probable pomacanthid hybrids, five are inCentropyge (C. eibli x C. flavissimus, C. eibli x C. vrolikii, C. flavissimus x C. vrolikii, C. loricu0lus x C. potteri, andC. multifasciatus x C. venustus); one inHolacanthus (H. bermudensis x H. ciliaris), and four inPomacanthus (P. arcuatus x P. paru, P. chrysurus x P. maculosus, P. maculosus x P. semicirculatus, andP. sexstriatus x P. xanthometapon). An additional five examples of possible pomacanthid hybrids are described, two inCentropyge, two inChaetodontoplus and one inPomacanthus. Examination of hybrids may provide clues on reproductive behavior, dispersal capabilities, and phylogenetic relationships of species. More studies on hybridization in coral reef fish species, particularly those involving molecular techniques, are needed.     

Effects of chorda-lingual nerve injury and repair on human taste

Citric acid detection threshold and magnitude response weremeasured on the anterior tongue in 10 patients with unilateralchorda-lingual nerve transections before and after repair. Fungiformtaste buds were analysed by videomicroscopy. Preliminary datasuggests that humans can regenerate fungiform taste buds andrecover some taste sensitivity after repair.     

The effect of age on the recognition thresholds of three sweeteners: sucrose,saccharin and aspartame

It iS believed that people's sensitivity to taste declines with age but the evidence is inconclusive. This study was designed to test the hypothesis that taste recognition thresholds (TRTs) for sweetness are higher in older than in younger individuals, using groups of 16 younger subjects (18–30) and 16 older subjects (60–85). Three test substances were used: sucrose, aspartame and saccharin. A questionnaire recorded variables which might have affected TRTs, but data failed to show any trend that might have biased the principle variate-age. There was a significant alteration with age of recognition thresholds, at least for sucrose and saccharin. The differences between the groups for the three sweeteners were due to the fact that all the very sensitive subjects were young. None of the older subjects had particularly poor discrimination: all but one had TRTs within the range of younger subjects. Although there are age-related taste changes, they are much less dramatic than commonly occurs with other senses, such as sight and hearing. The findings of this study have implications for institutional catering and the dietary management of older people using non-sugar sweeteners.     

Midgut proteinase activities of three keratinolytic larvae,Hofmannophila pseudospretella,Tineola bisselliella,and Anthrenocerus australis,and the effect of proteinase inhibitors on proteolysis

The midgut proteinase activities were characterized from the keratinolytic larvae of two lepidopterans, Hofmannophila pseudospretella (Stainton) (Oecophoridae) and Tineola bisselliella (Hummel) (Tineidae), and one coleopteran, Anthrenocerus australis (Hope) (Dermestidae). The major endopeptidase activities, characterized using specific enzyme inhibitors, were serine proteinases with hydrolytic activity against N-benzoyl-DL-arginine-p-nitroanilide and against N-succinyl-L-alanyl-L-alanyl-L-prolyl-L-leucine-p-nitroanilide. No significant levels of metalloendopeptidase or cysteine endopeptidase activities were detected. Aminopeptidase activity was present in all larvae. The enzyme levels and properties of the two moth larvae were similar to each other and to those of phytophagous lepidopteran larvae but different from those of the beetle larva. Whereas only a limited number of serine proteinase inhibitors inhibited the midgut proteolysis of the lepidopteran larvae, most inhibitors inhibited the midgut proteolysis of the beetle larva. © 1994 Wiley-Liss, Inc.     

1.56 Å structure of mature truncated human fibroblast collagenase

The X-ray crystal structure of a 19 kDa active fragment of human fibroblast collagenase has been determined by the multiple isomorphous replacement method and refined at 1.56 Å resolution to an R-factor of 17.4%. The current structure includes a bound hydroxamate inhibitor, 88 waters and three metal atoms (two zincs and a calcium). The overall topology of the enzyme, comprised of a five stranded β-sheet and three α-helices, is similar to the thermolysin-like metalloproteinases. There are some important differences between the collagenase and thermolysin families of enzymes. The active site zinc ligands are all histidines (His-218, His-222, and His-228). The presence of a second zinc ion in a structural role is a unique feature of the matrix metalloproteinases. The binding properties of the active site cleft are more dependent on the main chain conformation of the enzyme (and substrate) compared with thermolysin. A mechanism of action for peptide cleavage similar to that of thermolysin is proposed for fibroblast collagenase. © 1994 Wiley-Liss, Inc.     

Localization of a New Type of X-Linked Liver Glycogenosis to the Chromosomal Region Xp22 Containing the Liver α-Subunit of Phosphorylase Kinase (PHKA2)

We describe here a new type of X-linked liver glycogen storage disease. The main symptoms include liver enlargement and growth retardation. The clinical and biochemical abnormalities of this glycogenosis are similar to those of classical X-linked liver glycogenosis due to phosphorylase kinase deficiency (XLG). However, in contrast to patients with XLG, the patients described here have no reduced phosphorylase kinase activity in erythrocytes and leukocytes, and no enzyme deficiency could be found. Linkage analysis of four families with this X-linked type of liver glycogenosis assigned the disease gene to Xp22. Lod scores obtained with the markers DXS987, DXS207, and DXS999 were 3.97, 2.71, and 2.40, respectively, all at 0% recombination. Multipoint linkage analysis localized the disease gene between DXS143 and DXS989 with a maximum lod score of 4.70 at θ = 0, relative to DXS987. As both the classical XLG gene and the liver α-subunit of PHK (PHKA2) are also located in Xp22, this variant type of XLG may be allelic to classical XLG, and both diseases may be caused by mutations in PHKA2. Therefore, we propose to classify XLG as XLG type I (the classical type of XLG) and XLG type II (the variant type of XLG).