A worldwide correlation of lactase persistence phenotype and genotypes

Background: The ability of adult humans to digest the milk sugar lactose - lactase persistence - is a dominant Mendelian trait that has been a subject of extensive genetic, medical and evolutionary research. Lactase persistence is common in people of European ancestry as well as some African, Middle Eastern and Southern Asian groups, but is rare or absent elsewhere in the world. The recent identification of independent nucleotide changes that are strongly associated with lactase persistence in different populations worldwide has led to the possibility of genetic tests for the trait. However, it is highly unlikely that all lactase persistence-associated variants are known. Using an extensive database of lactase persistence phenotype frequencies, together with information on how those data were collected and data on the frequencies of lactase persistence variants, we present a global summary of the extent to which current genetic knowledge can explain lactase persistence phenotype frequency. Results: We used surface interpolation of Old World lactase persistence genotype and phenotype frequency estimates obtained from all available literature and perform a comparison between predicted and observed trait frequencies in continuous space. By accommodating additional data on sample numbers and known false negative and false positive rates for the various lactase persistence phenotype tests (blood glucose and breath hydrogen), we also apply a Monte Carlo method to estimate the probability that known lactase persistence-associated allele frequencies can explain observed trait frequencies in different regions. Conclusion: Lactase persistence genotype data is currently insufficient to explain lactase persistence phenotype frequency in much of western and southern Africa, southeastern Europe, the Middle East and parts of central and southern Asia. We suggest that further studies of genetic variation in these regions should reveal additional nucleotide variants that are associated with lactase persistence

Inverse Limits On [0,1] Using Piecewise Linear Unimodal Bonding Maps

In this paper we investigate inverse limits on [0,1] using a single bonding map chosen from a two-parameter family of piecewise linear unimodal bonding maps. This investigation focuses on the parameter values at the boundary between a hereditarily decomposable inverse limit and an inverse limit containing an indecomposable continuum. © 1999 American Mathematical Society

Freeze probabilities and cumulative heat sums : their effect on Tennessee vegetable producers

One of the most critical decisions that a vegetable producer must make is the scheduling of planting and harvesting dates. V/hile many factors affect this scheduling process, air temperature is by far the most important. Late spring and early fall freezes can be devastating to vegetable crops. Since temperature in the field cannot be controlled by vegetable producers, they must schedule around the occurrence of freezing temperatures. To recognize the risks of freezing temperatures, producers should have access to various temperature probabilities. The purpose of this study was to use temperature data to assist Tennessee vegetable growers in the decision making process pertaining to crop selection, succession cropping, and alternative planting or harvesting dates. The data employed in this study were the daily high and low temperatures recorded at 75 weather collection stations in Tennessee. Isothermal maps of Tennessee that display temperature probability patterns were constructed. Additionally, isothermal maps of Tennessee that display heat unit accumulation patterns were constructed. The average number of calendar days required to accumulate targeted heat unit totals were ascertained and analyzed. The timing of production to enter certain market windows and/or to capture economies of production associated with sequential cropping may force producers to incorporate the risk of temperature-related crop damage into their farm management decisions. Findings in this study suggest that a substantial amount of extra freeze risk may be necessary to capture seasonally higher prices

Periodicity And Indecomposability

In this paper we characterize the existence of periodic points of odd period greater than one for unimodal mappings of an interval onto itself. The interesting juxtaposition of this condition with the occurrence in inverse limits of the well-known Brouwer-Janiszewski-Knaster continuum is explored. Also obtained is a characterization of indecomposability of certain inverse limits using a single unimodal bonding map. © 1995 American Mathematical Society

The mitochondrial basis of ageing and neurodegeneration

One of the greatest achievements of the past 150 years is the extraordinary extension of average human lifespan. However, increasing average lifespan is coupled to an insidious rise in age-related cognitive decline and muscle loss. Indeed, progressive age is the number one risk factor for non-communicable diseases. Understanding the underlying biological mechanisms which drive ageing is a mammoth task. Mitochondrial dysfunction has emerged as a critical feature of ageing. This Thesis explored the biochemical changes to mitochondria with age and diseases of age. Firstly, in mouse brain and muscle mitochondria, the expression of potential biological markers of ageing, carbonic anhydrase-II and -III were shown across adulthood. A window of increasing carbonic anhydrase expression between 12-18 months of age was identified. Targeted inhibition of C. elegans CA orthologue, cah-2, at middle age significantly increased lifespan. Treatment of C. elegans with the carbonic anhydrase-II inhibitor, dorzolamide hydrochloride, at middle age showed a trend toward increased lifespan, but this did not reach significance. Secondly, the long-lived bat (P. pipistrellus) was shown to have high levels of fatty acid binding protein 3 (FABP3) in muscle mitochondria, compared to short-lived mice. Increasing FABP3 levels was connected to high free fatty acid levels. Knockdown of FABP3 C. elegans orthologues altered mitochondrial morphology, oxygen consumption and significantly reduced lifespan. Thirdly, the healthspan promoting lifestyle intervention, exercise, was assessed. D. melanogaster were exercised on the bespoke Ingram Counterbalanced Exercise machine. The proteomic profiles of mitochondria isolated from exercised and non-exercised wild-type and Pink1-/- D. melanogaster were examined. The mitochondrial proteome displayed exercise-related changes. Interestingly, exercise caused sweeping mitochondrial protein expression reductions to Pink1-/- D. melanogaster with exercise. Fourthly, the cerebellar mitochondrial inflammatory marker profiles of females and males with and without Parkinson’s disease were surveyed. This study found that inflammatory marker changes manifest differently with disease progression between sexes. Interestingly, the control female group showed a distinctive inflammatory profile, characterised by highly variant inflammatory marker levels. This Thesis describes biochemical alterations to mitochondria with ageing and diseases of age. These findings highlight the diverse changes that mitochondria undergo with ageing, potential markers of longevity and interventions that may improve healthspan

Concerning periodic points in mappings of continua

In this paper we present some conditions which are sufficient for a mapping to have periodic points. © 1988 American Mathematical Society