THE RELATION BETWEEN DNA SYNTHESIS AND CHROMOSOME STRUCTURE AS RESOLVED BY X-RAY DAMAGE

Vicia faba root tip cells were treated for short periods with tritiated thymidine, either immediately before or after exposure of roots to x-rays, and autoradiograph preparations were analysed in an attempt to test the hypothesis that chromatid type (B') aberrations are induced only in those chromosome regions that have synthesized DNA prior to x-irradiation, whereas chromosome type (B') aberrations are induced only in unduplicated chromosome regions. Studying the relation between presence or absence of label at loci involved in aberrations, in cells irradiated at different development stages, and the pattern of labelling in cells carrying both types of aberration leads to the conclusion that B' aberrations are induced only in unreplicated chromosome regions. Following replication, only B' aberrations are induced, but these aberrations are also induced in chromosome regions preparing to incorporate DNA. It is suggested that the doubled response of the chromosome to x-rays prior to DNA incorporation might reflect a physical separation of replicating units prior to replication. The aberration yields in damaged cells which were irradiated in G₁ S, and early G₂ were in the ratio of 1.0:2.0:3.2. The data indicate that the increased yield of B' in early G₂ relative to S cells may be a consequence of changes in the spatial distribution of the chromosomes within the nucleus.     

Demography,group composition,and dispersal in wild cotton-top tamarin (Saguinus oedipus) groups

Groups of individually marked cotton-top tamarins (Saguinus oedipus), located in La Reserva Forestal Protectora Serranía de Coraza-Montes de María in Colosó Colombia, were studied over a period of 5 years. Data on group composition, stability, birthing seasons, and dispersal patterns are used to examine the reproductive strategies and tactics used by males and females. Both monogamous groups and groups containing two pregnant females have been observed. All groups contained at least one adult female and male, with several groups containing several adult males and females. Both males and females dispersed to neighboring groups, and there were no sex differences in rates of emigration. Males were more likely to immigrate into a new group following the death/emigration of a resident male. Females appeared to tolerate immigrating females but would actively defend their breeding position during fertile periods. © 1996 Wiley-Liss, Inc.     

Determining fine‐scale migratory connectivity and habitat selection for a migratory songbird by using new GPS technology

Migratory aerial insectivores are among the fastest declining avian groups, but our understanding of these trends has been limited by poor knowledge of migratory connectivity and the identification of critical habitat across the vast distances they travel annually. Using new, archival GPS loggers, we tracked individual purple martins Progne subis from breeding colonies across North America to determine precise (< > 10 m) locations of migratory and overwintering roost locations in South America and to test hypotheses for fine‐scale migratory connectivity and habitat use. We discovered weak migratory connectivity at the roost scale, and extensive, fine‐scale mixing of birds in the Amazon from distant (> 2000 km) breeding sites, with some individuals sharing the same roosting trees. Despite vast tracts of contiguous forest in this region, birds occupied a much more limited habitat, with most (56%) roosts occurring on small habitat islands that were strongly associated with water. Only 17% of these roosts were in current protected areas. These data reflect a critical advance in our ability to remotely determine precise migratory connectivity and habitat selection across vast spatial scales, enhancing our understanding of population dynamics and enabling more effective conservation of species at risk.     

Effects of reproductive and social context on vocal communication in captive female African elephants (Loxodonta africana)

Female African elephants advertise changes in reproductive condition to males through a variety of modalities, including an increase in low‐frequency vocalizations, presumed to travel long distances. Although males respond to these vocalizations, it has been suggested that their proximate function may be to signal to nearby females rather than to distant males. Because elephants live in a female‐bonded society, it is likely that changes in female reproductive condition also affect close‐range interactions between high‐ and low‐ranking females and that vocalizations may mediate these interactions. To examine female–female interactions related to vocal production and the ovulatory cycle, this year‐long study monitored behavior, vocalizations and hormonal cycles for a group of six female captive African elephants at Disney's Animal Kingdom. Rates of several types of close‐range interactions were observed to change over the phases of the estrous cycle, and rank seemed to affect whether or not low‐frequency vocalizations were given in association with these interactions. Results of this study suggest that a female African elephant's immediate social context and rank in the social hierarchy interact with the hormonal cycle in the production of low‐frequency vocalizations, thus many of these vocalizations may not function proximately as signals to distant males, but may be a result of the changing dynamics among females. Zoo Biol 0:1–17, 2005. © 2005 Wiley‐Liss, Inc.     

A proteomics approach to cloning fenestrin from the nuclear exchange junction of tetrahymena

ABSTRACT. We set out to find the " fenestrin " gene, a gene whose protein is associated with numerous cellular apertures, including the nuclear exchange junction in mating Tetrahymena thermophila . First we developed protocols for imaging and isolating intact nuclear exchange junctions from conjugating cells. Proteins from these junctions were purified using SDS-PAGE, subjected to limited proteolysis, and precise molecular weights were determined by mass spectrometry. Using Protein Prospector^® software and the published Tetrahymena Genome Database, genes for 15 of the most abundant proteins found in our extracts were identified. The most promising candidate was cloned by PCR, fused to yellow fluorescent protein (YFP), and placed under the control of an inducible metallothionein promoter. YFP-localization within live Tetrahymena transformants strongly suggested that one of these genes encoded the fenestrin protein, a result that was subsequently confirmed by Western blotting.