Population growth of a gorgonian coral: equilibrium and non-equilibrium sensitivity to changes in life history variables

Summary A size dependent model of population growth of the Caribbean gorgonian Plexaura A is developed based on observed rates of survival, growth and colony fragmentation at a site in the San Blas Islands, Panama. Sensitivity and elasticity analyses indicate that the fate of large colonies has the greatest effect on population growth. Variables which directly affect the generation of large colonies have the next greatest effect on population growth. These variables include the recruitment of large fragments, and the survivorship of colonies in the next smaller size class. Sexual reproduction has an extremely limited ability to affect population growth. Vegetative reproduction has a greater potential effect on growth rates. Environmental conditions regularly change the matrix of transition probabilities which predicts population growth. This keeps the population from approaching its stable size class distribution. Deviations from the stable size class distribution alter sensitivity and elasticity and in this case have the effect of increasing the importance of survivorship of the smallest colonies. Nonequilibrium conditions alter sensitivity analyses and it is important to assess whether populations are at equilibrium and to determine the effects of such deviations on the sensitivity analysis.     

Peroxidative oxidation of bilirubin during prostaglandin biosynthesis

The peroxidative oxidation of bilirubin has been characterized in the ram seminal vesicle microsomal system. The oxidation was monitored by following the loss in absorbance of bilirubin at 440 nm. Bilirubin behaves as a peroxidase substrate for prostaglandin H synthase. The oxidation may be initiated by the addition of arachidonic acid or peroxides to incubations containing ram seminal vesicle microsomes and bilirubin, and is sensitive to inhibition by reduced glutathione. The arachidonate-dependent oxidation, but not the peroxide-initiated case, is inhibited by indomethacin. Similar results were obtained using microsomal preparations from mouse, rat, and pig lungs. Spectral and chromatographic examination of the products of bilirubin oxidation in the ram seminal vesicle system demonstrate that biliverdin is produced in this system by the dehydrogenation of bilirubin, but that this product accounts for only about 15% of the bilirubin consumed. Biliverdin itself is not oxidized in this system. At least three highly polar, fluorescent products also are formed from bilirubin. Though not identified, these polar products differ markedly in chromatographic behavior from the major fluorescent products obtained following the singlet oxygen oxidation or the autoxidation of bilirubin.     

Beta-aminoisobutyric acid (BAIB) excretion in urine of residents of eight communities in the states of Michoacán and Oaxaca, Mexico

The ratio of β-aminoisobutyric acid to neutral amino acids (BAIB/N) in urine was determined in 474 Mexicans from three communities in the state of Michoacán and five in Oaxaca. The frequency curves vary significantly between the three communities in Michoacán and between the two states. The proportion of high excretors (BAIB/N 0.300) varies from 14 to 41% (all intermediate between European white and North American Indian values), but were generally higher in the more “Indian” communities.     

Comparison of the separation of Candida albicans chromosome-sized DNA by pulsed-field gel electrophoresis techniques.

Pulsed-field gel electrophoresis techniques were used to study chromosome-sized DNA molecules of C. albicans. Chromosome-sized DNA of two strains of Candida albicans has been resolved into 8 bands by orthogonal-field-alternation gel electrophoresis (OFAGE). Six bands were observed in chromosomal preparations of C. albicans using field-inversion gel electrophoresis (FIGE). Differences in the electrophoretic mobilities of bands of the strains of C. albicans examined suggests that chromosome-length polymorphisms exist and make it difficult to correlate the banding patterns among strains. These correlations were facilitated, however, by assignment of C. albicans chromosomes by hybridization using a collection of cloned DNA probes specific for each of the 8 observed bands. Southern blotting showed that the 6 FIGE bands consisted of 4 singlets and 2 comigrating doublets, accounting for the 8 bands observed by OFAGE analysis. The agreement between OFAGE and FIGE analysis suggests that the C. albicans haploid genome contains a minimum of 8 chromosomes.     

Three-dimensional species distribution modelling reveals the realized spatial niche for coral recruitment on contemporary Caribbean reefs

The three-dimensional structure of habitats is a critical component of species' niches driving coexistence in species-rich ecosystems. However, its influence on structuring and partitioning recruitment niches has not been widely addressed. We developed a new method to combine species distribution modelling and structure from motion, and characterized three-dimensional recruitment niches of two ecosystem engineers on Caribbean coral reefs, scleractinian corals and gorgonians. Fine-scale roughness was the most important predictor of suitable habitat for both taxa, and their niches largely overlapped, primarily due to scleractinians' broader niche breadth. Crevices and holes at mm scales on calcareous rock with low coral cover were more suitable for octocorals than for scleractinian recruits, suggesting that the decline in scleractinian corals is facilitating the recruitment of octocorals on contemporary Caribbean reefs. However, the relative abundances of the taxa were independent of the amount of suitable habitat on the reef, emphasizing that niche processes alone do not predict recruitment rates.     

mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species

Reconstructions of the human-African great ape phylogeny by using mitochondrial DNA (mtDNA) have been subject to considerable debate. One confounding factor may be the lack of data on intraspecific variation. To test this hypothesis, we examined the effect of intraspecific mtDNA diversity on the phylogenetic reconstruction of another Plio- Pleistocene radiation of higher primates, the fascicularis group of macaque (Macaca) monkey species. Fifteen endonucleases were used to identify 10 haplotypes of 40-47 restriction sites in M. mulatta, which were compared with similar data for the other members of this species group. Interpopulational, intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of divergence time and branching order incorporating this variation were substantially different from those based on single representatives of each species. We conclude that intraspecific mtDNA diversity is substantial in at least some primate species. Consequently, without prior information on the extent of genetic diversity within a particular species, intraspecific variation must be assessed and accounted for when reconstructing primate phylogenies. Further, we question the reliability of hominoid mtDNA phylogenies, based as they are on one or a few representatives of each species, in an already depauperate superfamily of primates.      

Characterization of a novel gene for strain typing reveals substructuring of Aspergillus fumigatus across North America

Fifty-five epidemiologically linked Aspergillus fumigatus isolates obtained from six nosocomial outbreaks of invasive aspergillosis were subtyped by sequencing the polymorphic region of the gene encoding a putative cell surface protein, Afu3g08990 (denoted as CSP). Comparative sequence analysis showed that genetic diversity was generated in the coding region of this gene by both tandem repeats and point mutations. Each unique sequence in an outbreak cluster was assigned an arbitrary number or CSP sequence type. The CSP typing method was able to identify "clonal" and genotypically distinct A. fumigatus isolates, and the results of this method were concordant with those of another discriminatory genotyping technique, the Afut1 restriction fragment length polymorphism typing method. The novel single-locus sequence typing (CSP typing) strategy appears to be a simple, rapid, discriminatory tool that can be readily shared across laboratories. In addition, we found that A. fumigatus isolates substructured into multiple clades; interestingly, one clade consisted of isolates predominantly representing invasive clinical isolates recovered from cardiac transplant patients from two different outbreak situations. We also found that the A. fumigatus isolate Af293, whose genome has been sequenced, possesses a CSP gene structure that is substantially different from those of the other A. fumigatus strains studied here, highlighting the need for further taxonomic study.     

Proteomics approach to identifying ATP-covalently modified proteins

This study aims to investigate functionally similar proteins based on their capacity to remain bound to ATP under stringent resolving conditions. Using two-dimensional gel electrophoresis and capillary liquid chromatography on-line mass spectrometry, we have identified several mammalian and E. coli proteins that appear to covalently bind ATP. To validate this approach, we obtained commercially purified forms of proteins identified from two-dimensional protein maps and tested their capacity to bind alpha 32P phosphate labeled ATP. This proteomics approach provides an initial screening method of identifying functionally similar proteins for further scrutiny by a more traditional analysis.