Genetic differentiation among populations of Caridinazebra (Decapoda: Atyidae) in tropical rainforest streams, northern Australia

1. Caridina zebra is a common atyid shrimp in some tropical rainforest streams in far north Queensland, Australia. Genetic variation at five allozyme loci was used to estimate the level of dispersal among populations of this species, within and between stream systems. Shrimps were sampled from nine streams in the Tully River catchment and two headwater streams in the adjacent Herbert River catchment in an area under consideration for extensive hydroelectric development.
2. High levels of genetic differentiation were recorded among most populations which suggests that, like other fully aquatic species, movement is limited to a very small spatial scale.
3. In the Tully catchment, populations of shrimp from streams with confluences at high altitude showed less genetic differentiation than those from streams which directly entered the lower river. Dispersal between the latter streams is clearly limited by the presence of large waterfalls and cascades.
4. Adjacent stream populations were often highly differentiated, despite their close proximity, suggesting that overland dispersal is unlikely. However, populations of shrimp in the two streams in the Herbert catchment were strikingly similar in genetic structure to those in adjacent headwater streams of the Tully. Such similarity may reflect relatively recent changes in drainage patterns.     

Population density of the Réunion Grey White-eye Zosterops borbonicus within the summit ecosystems of Réunion,Mascarene Islands

Assessing population density is crucial for studying the ecology and evolutionary biology of species as well as for conservation purposes. Here we used point count methods to infer population density in a single-island endemic passerine bird, the Réunion Grey White-eye Zosterops borbonicus, that displays striking evidence of differentiation at a small spatial scale. Population density was estimated at 5.17 birds ha^?1 (CL 4.85–5.50), a value somewhat higher than previously believed. This estimation provides the first detailed estimation of bird population density in the vulnerable summit ecosystems of Réunion and will possibly allow a better understanding of the evolutionary causes of this plumage colour variation.     

Differential effects of gabaculin and laevulinic acid on protochlorophyllide regeneration

Abstract The effects of gabaculin (3-amino 2,3-dihydrobenzoic acid) and laevulinic acid on the regeneration of protochlorophyllide from exogenous δ-aminolaevulinic acid in leaves of dark-grown barley (Hordeum vulgare) after a brief light treatment were compared. Gabaculin, a potent inhibitor of chlorophyll biosynthesis, did not inhibit this process showing that it affects the formation of δ-aminolaevulinic acid rather than its further metabolism. Laevulinic acid, which is an inhibitor of δ-aminolaevulinic acid dehydratase, prevented regeneration of protochlorophyllide provided pools of intermediates in the biosynthetic sequence were depleted. Formation of relatively large amounts of protochlorophyllide in some experiments suggests a lack of control in the utilization of δ-aminolaevulinic acid for protochlorophyllide synthesis.     

A red/white selection for Saccharomyces cerevisiae auxotrophs

Red pigment production in yeast cells with adel or ade2 mutations has been exploited to develop a method of identifying specific amino acid auxotrophs. Amino acid auxotrophs carrying mutations in adel or ade2 show delayed pigment production at sub-optimal amino acid levels. This delay allows selection of amino acid auxotrophs following mutagenesis, since red pigment is produced in prototrophs whilst auxotrophs remain white. This differential colour reaction has been applied to select leucine, lysine and serine auxotrophs. Large numbers of colonies could easily be screened without the need for extensive replica plating.     

Plasma neurotensin release and gastric emptying in the dumping syndrome

Seventy-three patients were studied after ingesting a liquid glucose meal, tagged with ¹¹³Indium. Nineteen of these patients were awaiting surgery for their duodenal ulcer, while 54 were studied postoperatively, 25 of whom experienced troublesome postprandial (dumping) symptoms in their daily lives. The radioactive marker emptied significantly faster in the symptomatic patients than in the symptomfree, pre and post-operative groups (initial emptying rate 3.45 ± 0.23, compared with 1.16 ± 0.19 and 1.27 ± 0.15% fall in counts/min respectively; p < 0.01). Initial (20 min) rises in the plasma concentrations of neurotensin-like immunoreactivity measured during the test correlated significantly with the rate of gastric emptying in all patients, being greatest in patients with dumping symptoms. Physiological concentrations of neurotensin have been shown to delay gastric emptying. The excessive rise in plasma neurotensin-like immunoreactivity in patients with dumping symptoms, presumably occuring as a result of the rapid passage of nutrients to the neurotensin-rich ileum, may possibly have a compensatory role in slowing further emptying from the stomach.     

Induction of the Feline Oncornavirus Associated Cell Membrane Antigen in Human Cells

BY N-terminal amino-acid sequence analysis, Glenner et al.¹ have shown that amyloid fibrils are very similar to the variable part of an immunoglobulin kappa light chain (Bence-Jones protein Ker) and they suggested that amyloid is constituted by immunoglobulin light chains.     

Molecular evidence for the rapid propagation of mouse t haplotypes from a single, recent, ancestral chromosome

Mouse t haplotypes are variant forms of chromosome 17 that exist at high frequencies in worldwide populations of two species of commensal mice. To determine both the relationship of t haplotypes to each other and the species within which they exist, 35 representative t haplotypes were analyzed by means of 10 independent molecular probes, including five DNA clones and five polypeptide spots identified by means of two- dimensional gel electrophoresis. All of the tested haplotypes were found to share restriction fragments and polypeptide spots that are absent in mice carrying wild-type forms of chromosome 17. This observation provides the first direct evidence that all of the known t haplotypes are descendents of a single ancestral chromosome. The absence of variation among t haplotypes could mean that this ancestral chromosome existed relatively recently, in which case it would be necessary to postulate introgressions of t haplotypes across species lines to explain their presence in both Mus domesticus and M. musculus. Alternatively, it is possible that the ancestral chromosome existed prior to the split between M. domesticus and M. musculus and that, by chance, our probes fail to detect polymorphisms that exist among the t haplotypes. A further result of our analysis is the characterization of a partial t haplotype in a wild population of Israeli mice.      

Litter inputs to a tropical Australian rainforest stream

Abstract Vertical litterfall and lateral litter movement were monitored in the riparian zone of Birthday Creek, a small upland rainforest stream in north Queensland, from June 1987 to May 1990. Total litterfall (mean = 484 g m^?2 year-1) was low in comparison with other tropical sites both within Australia and elsewhere. Litterfall was distinctly seasonal, with maxima occurring in the spring (October-November) and minima in winter (June–July). Tropical storms caused short-term increases in litterfall, especially of the small wood fraction. Overall, laterally transported litter contributed 6.8% of the total litter input to the monitored section of the stream. Lateral movement varied according to bank slope and microtopographic features and was not related to wind. Nitrogen and phosphorus concentration of leaves were low (mean N= 1.26%, P = 0.029% by weight). Nitrogen concentration of laterally transported levels overall was about 19% higher than that of leaves falling directly into the stream.