Between estuaries and the sea

Dissolved and particulate materials and living organisms are exchanged between estuaries and the sea. Net material fluxes, import or export, appear to depend on physical and biological processes within both estuarine and coastal ecosystems. In temperate zone lagoonal systems, the marsh-estuarine continuum hypothesis can provide a reasonable synthetic explanation of transport based on the level of ecosystem maturity within the system. The relative importance of riverine and lagoonal material exchanges with the coastal ocean are at present entirely speculative and make the estimation of the regional influences of material transports between estuaries and the coastal ocean uncertain. Organismic exchanges depend on both passive and active behavior mechanisms and are species specific. Few quantitative estimates of organismic fluxes exist and the role of non-commercial invertebrates and fish in these fluxes are unknown.     

Birth and simultaneous rearing of two litters in a pack of captive African wild dogs (Lycaon pictus)

Two female African wild dogs (Lycaon pictus) in a pack of 10 animals at the Bronx Zoo gave birth to litters of nine and seven pups within a 2‐day period. Two pups from the litter of seven died before they were 2 weeks old, but the other 14 survived past weaning. Litter size, sex ratio, and pup developmental stages were all consistent with data obtained from other captive‐ and wild‐born litters. Both dams were very attentive to their litters, and during the pups' first 2 weeks spent >90% of their time in the dens with the pups. By 2 days after birth and during their first 2 weeks of life, the pups spent 86% of their time in a nursing position. Before parturition and during the first week post‐partum, one of the dams (DAL) was clearly dominant to the other (WHI). However, the females' dominance rank reversed 2 weeks post‐partum. On two occasions during the pups' first 2 weeks DAL stole and reared one of WHI's pups, but between Weeks 3 and 4 all of DAL's pups were stolen and WHI raised both litters as one until they were weaned. The pups began spending time out of their den at approximately 1 month of age. The timing of the births, the design of the wild dogs' management facility, and the presence of several dens in different enclosures within the facility all likely contributed to the successful rearing of the litters. The pups in both litters were very similar in size because of the short interval between births, so one litter did not have a competitive advantage over the other with respect to gaining access to the dam for milk. The facility's design helped mitigate aggression within the pack, and the presence of multiple dens enabled to dams to move the pups to different den sites and allowed the two females to stay visually and spatially apart from each other while remaining with the pack. Zoo Biol 0:1–17, 2006. © 2006 Wiley‐Liss, Inc.     

The Genetic Basis of Metal Hyperaccumulation in Plants

Referee: Professor Alan J.M. Baker, School of Botany, The University of Melbourne, VIC 3010, Australia A relatively small yet diverse group of plants are capable of sequestering metals in their shoot tissues at remarkably high concentrations that would be toxic to most organisms. This process, known as metal hyperaccumulation, is of interest for several reasons, including its relevance to the phytoremediation of metalpolluted soils. Most research on hyperaccumulators has focused on the physiological mechanisms of metal uptake, transport, and sequestration, but relatively little is known regarding the genetic basis of hyperaccumulation. There are no known cases of major genetic polymorphisms in which some members of a species are capable of hyperaccumulation and others are not. This is in contrast to the related phenomenon of metal tolerance, in which most species that possess any metal tolerance are polymorphic, evolving tolerance only in local populations on metalliferous soil. However, although some degree of hyperaccumulation occurs in all members of the species that can hyperaccumulate, there is evidence of quantitative genetic variation in ability to hyperaccumulate, both between and within populations. Such variation does not appear to correlate positively with either the metal concentration in the soil or the degree of metal tolerance in the plant. Studies using controlled crosses, interspecific hybrids, and molecular markers are beginning to shed light on the genetic control of this variation. As molecular physiology provides greater insights into the specific genes that control metal accumulation, we may learn more about the genetic and regulatory factors that influence variable expression of the hyperaccumulation phenotype.     

A molecular basis for retinol stimulation of vesicle budding in vivo and in vitro

Retinol stimulates the formation of transition vesicles in situ and in all free systems based on rat liver. The stimulation is on vesicle formation from transitional endoplasmic reticulum and not on vesicle fusion with donor membranes. Vesicle budding in the cell free system requires a nucleoside triphosphate and is sensitive to inhibition by thiol reagents. In this report we develop and test a model whereby a retinol-modulated NADH:protein disulfide reductase (NADH oxidase) with protein disulfide-thiol interchange activity is implicated in the vesicle budding mechanism. The protein has the ability to restore activity to scrambled, inactive RNase A and is stimulated or inhibited by retinol depending on the redox environment. Under reducing conditions and in the presence of a chemical reductant such as GSH, the partial reaction stimulated by retinol appears to be the oxidation of membrane disulfides. This is the first report of an enzymatic mechanism to explain specific retinol effects both in vivo and in vitro on membrane trafficking not given by retinoic acid.