Integrated life science education in Bachelor of Nursing and Bachelor of Chinese Medicine at The University of Hong Kong

poster presentation no. PP54published_or_final_versio

Pre-Whaling Genetic Diversity and Population Ecology in Eastern Pacific Gray Whales: Insights from Ancient DNA and Stable Isotopes

Commercial whaling decimated many whale populations, including the eastern Pacific gray whale, but little is known about how population dynamics or ecology differed prior to these removals. Of particular interest is the possibility of a large population decline prior to whaling, as such a decline could explain the ∼5-fold difference between genetic estimates of prior abundance and estimates based on historical records. We analyzed genetic (mitochondrial control region) and isotopic information from modern and prehistoric gray whales using serial coalescent simulations and Bayesian skyline analyses to test for a pre-whaling decline and to examine prehistoric genetic diversity, population dynamics and ecology. Simulations demonstrate that significant genetic differences observed between ancient and modern samples could be caused by a large, recent population bottleneck, roughly concurrent with commercial whaling. Stable isotopes show minimal differences between modern and ancient gray whale foraging ecology. Using rejection-based Approximate Bayesian Computation, we estimate the size of the population bottleneck at its minimum abundance and the pre-bottleneck abundance. Our results agree with previous genetic studies suggesting the historical size of the eastern gray whale population was roughly three to five times its current size

Using Classical Population Genetics Tools with Heterochroneous Data: Time Matters!

BACKGROUND:New polymorphism datasets from heterochroneous data have arisen thanks to recent advances in experimental and microbial molecular evolution, and the sequencing of ancient DNA (aDNA). However, classical tools for population genetics analyses do not take into account heterochrony between subsets, despite potential bias on neutrality and population structure tests. Here, we characterize the extent of such possible biases using serial coalescent simulations. METHODOLOGY/PRINCIPAL FINDINGS:We first use a coalescent framework to generate datasets assuming no or different levels of heterochrony and contrast most classical population genetic statistics. We show that even weak levels of heterochrony ( approximately 10% of the average depth of a standard population tree) affect the distribution of polymorphism substantially, leading to overestimate the level of polymorphism theta, to star like trees, with an excess of rare mutations and a deficit of linkage disequilibrium, which are the hallmark of e.g. population expansion (possibly after a drastic bottleneck). Substantial departures of the tests are detected in the opposite direction for more heterochroneous and equilibrated datasets, with balanced trees mimicking in particular population contraction, balancing selection, and population differentiation. We therefore introduce simple corrections to classical estimators of polymorphism and of the genetic distance between populations, in order to remove heterochrony-driven bias. Finally, we show that these effects do occur on real aDNA datasets, taking advantage of the currently available sequence data for Cave Bears (Ursus spelaeus), for which large mtDNA haplotypes have been reported over a substantial time period (22-130 thousand years ago (KYA)). CONCLUSIONS/SIGNIFICANCE:Considering serial sampling changed the conclusion of several tests, indicating that neglecting heterochrony could provide significant support for false past history of populations and inappropriate conservation decisions. We therefore argue for systematically considering heterochroneous models when analyzing heterochroneous samples covering a large time scale

The First Molecular Phylogeny of Strepsiptera (Insecta) Reveals an Early Burst of Molecular Evolution Correlated with the Transition to Endoparasitism

A comprehensive model of evolution requires an understanding of the relationship between selection at the molecular and phenotypic level. We investigate this in Strepsiptera, an order of endoparasitic insects whose evolutionary biology is poorly studied. We present the first molecular phylogeny of Strepsiptera, and use this as a framework to investigate the association between parasitism and molecular evolution. We find evidence of a significant burst in the rate of molecular evolution in the early history of Strepsiptera. The evolution of morphological traits linked to parasitism is significantly correlated with the pattern in molecular rate. The correlated burst in genotypic-phenotypic evolution precedes the main phase of strepsipteran diversification, which is characterised by the return to a low and even molecular rate, and a period of relative morphological stability. These findings suggest that the transition to endoparasitism led to relaxation of selective constraint in the strepsipteran genome. Our results indicate that a parasitic lifestyle can affect the rate of molecular evolution, although other causal life-history traits correlated with parasitism may also play an important role

Systematic and Evolutionary Insights Derived from mtDNA COI Barcode Diversity in the Decapoda (Crustacea: Malacostraca)

Background: Decapods are the most recognizable of all crustaceans and comprise a dominant group of benthic invertebrates of the continental shelf and slope, including many species of economic importance. Of the 17635 morphologically described Decapoda species, only 5.4% are represented by COI barcode region sequences. It therefore remains a challenge to compile regional databases that identify and analyse the extent and patterns of decapod diversity throughout the world. Methodology/Principal Findings: We contributed 101 decapod species from the North East Atlantic, the Gulf of Cadiz and the Mediterranean Sea, of which 81 species represent novel COI records. Within the newly-generated dataset, 3.6% of the species barcodes conflicted with the assigned morphological taxonomic identification, highlighting both the apparent taxonomic ambiguity among certain groups, and the need for an accelerated and independent taxonomic approach. Using the combined COI barcode projects from the Barcode of Life Database, we provide the most comprehensive COI data set so far examined for the Order (1572 sequences of 528 species, 213 genera, and 67 families). Patterns within families show a general predicted molecular hierarchy, but the scale of divergence at each taxonomic level appears to vary extensively between families. The range values of mean K2P distance observed were: within species 0.285% to 1.375%, within genus 6.376% to 20.924% and within family 11.392% to 25.617%. Nucleotide composition varied greatly across decapods, ranging from 30.8 % to 49.4 % GC content. Conclusions/Significance: Decapod biological diversity was quantified by identifying putative cryptic species allowing a rapid assessment of taxon diversity in groups that have until now received limited morphological and systematic examination. We highlight taxonomic groups or species with unusual nucleotide composition or evolutionary rates. Such data are relevant to strategies for conservation of existing decapod biodiversity, as well as elucidating the mechanisms and constraints shaping the patterns observed.FCT - SFRH/BD/25568/ 2006EC FP6 - GOCE-CT-2005-511234 HERMESFCT - PTDC/MAR/69892/2006 LusomarBo

Further evaluation of first morning urinary oestrogen in monitoring gonadotrophin therapy

Efficient gonadotrophin therapy requires both biochemical and ultrasonic measurements of ovarian response. Biochemical monitoring can take the form of measurement of plasma oestradiol levels or urinary oestrogen excretion. Levels of first morning urinary oestrogen to creatinine ratio have been shown to correlate well with 24-hour total urinary oestrogen excretion. Such urine collection is not cumbersome and is less invasive than daily venepuncture. Eighty gonadotrophin treatment cycles were evaluated by first morning urinary oestrogen to creatinine ratio and ultrasound scanning of follicles. Analysis confirmed that the ratio correlated significantly both with plasma oestradiol and 24-hour urinary oestrogen levels. The administration of the ovulating dose of human chorionic gonadotrophin depended primarily on ultrasonic demonstration of the presence of mature follicles in the ovaries. There was no increased incidence of multiple gestation or hyperstimulation syndrome in 135 treatment cycles. It is concluded that first morning urinary oestrogen to creatinine ratio is a convenient and cheap method of efficient biochemical monitoring of ovarian response to gonadotrophin therapy.link_to_subscribed_fulltex

Immunoreactive β-endorphin in human seminal plasma

Seminal plasma beta-endorphin (β-EP) levels were determined by radioimmunoassay in 119 semen samples collected from fertile, infertile and healthy single young men without previously proven fertility histories. There were considerable amounts of β-EP in human seminal plasma, although the mean levels were not significantly different in the three groups. No significant correlations were found between the seminal plasma β-EP levels and individual parameters of general spermatozoal characteristics and in vitro spermatozoal fertilizing capacity. In fertile men, the levels of β-EP, FSH and LH in seminal plasma were significantly higher, whereas levels of T were significantly lower than those in serum. No significant correlations were observed between β-EP and other reproductive hormones in seminal plasma or serum. These findings confirm the presence of β-EP in seminal plasma and its local production is implicated. Whether there is a potential function of β-EP in semen on spermatozoal capacitation and fertilization in vivo, however, cannot be inferred from the present study.link_to_subscribed_fulltex

Comparative study of total urinary oestrogen and first morning urinary oestrogen in monitoring gonadotrophin therapy

Total 24-hour urinary oestrogen has been used extensively and proven to be reliable in monitoring gonadotrophin therapy for induction of ovulation. However, the method is time consuming for the patient and incomplete collection, as expected, is not uncommon, hence interfering with the treatment result. Oestrone-3-glucuronide in first morning urine samples has been shown to correlate well with plasma oestradiol-17 β levels during normal menstrual cycles. A comparative study was made to examine the correlation between the levels of 24-hour urinary oestrogen and first morning urinary oestrogen in patients on gonadotrophin therapy. Creatinine levels were also determined to exclude the factor of variable excretion of oestrogen. The correlation thus found is highly significant (p < 0.001). Hence first morning urinary oestrogen to creatinine ratios may be used to replace 24-hour urinary oestrogen in biochemical monitoring of gonadotrophin therapy,link_to_subscribed_fulltex

Effect of reserpine on fertilizing capacity of human spermatozoa

The effect of reserpine at various concentrations (2 x 10-6, 2 x 10-7, 2 x 10-8, 2 x 10-9 and 2 x 10-10M) on the in vitro fertilizing capacity of human spermatozoa was studied. Spermatozoa collected from presumably fertile men were washed in BWW medium and incubated with different concentrations of reserpine for 5 hr before insemination of the zona-free hamster ova. The spermatozoa penetration of the zona-free hamster ova was scored 6 hr later and the results were analyzed statistically. Reserpine, at all the concentrations tested, caused a significant dose-dependent decrease in the penetration of the denuded hamster ova in comparison to the control (p 0.05). These findings indicate that reserpine can affect the fertilizing capacity of human spermatozoa in vitro and provide an additional evidence to suggest the prospective use of reserpine as a vaginal contraceptive. | The effect of reserpine at various concentrations (2x10-6, 2x10-7 2x10-8, 2x10-9, and 2x10-10 m) on the in vitro fertilizing capacity of human spermatozoa was studied. Spermatozoa was collected from presumably fertile men and washed in BWW medium and incubated with different concentrations of reserpine for 5 hours prior to insemination of the zona-free hamster ova. The spermatozoal penetration of the zona-free hamster ova was scored 6 hours later and results were analyzed statistically. Reserpine, at all concentrations tested, caused a significant dose-dependent decrease in the penetration of the denuded hamster ova in comparison to the control (P0.05). The percent motility of spermatozoa decreased as a function of time during the preincubation period to initiate spermatozoal capacitation but there were no significant differences in the values between the control and the reserpine-treated sprmatozoa (P0.05). These findings indicate that reserpine can affect the fertilizing capacity of human spermatozoa in vitro and provide additional evidence to suggest the prospective use of reserpine as a vaginal contraceptive. author's modifiedlink_to_subscribed_fulltex

Spermatozoal characteristics of hyperspermic and hypospermic human semen samples

Studies of general semen characteristics and in vitro spermatozoal fertilizing capacities of 45 hyperspermic and 91 hypospermic human semen samples failed to demonstrate significant correlations (p > 0.05) between the sperm count, percentage of motile sperms, or percentage with normal morphology and the zona-free hamster ova penetration rate in both groups. Impaired fertility in these patients is believed to be a reflection of defects in the quantity and quality of spermatozoa after insemination in the vagina rather than those detected after ejaculation.link_to_subscribed_fulltex