Unusual supernumerary chromosomes: types encountered in a referred population,and high incidence of associated maternal chromosome abnormalities

Summary In a 6-year period 128 patients with supernumerary autosomes were identified in our laboratory. The majority had primary trisomy, but 19 (15%) had extra, unusual chromosomes, not just a normal chromosome present in an extra copy. Of these, 18 were complex and did not resemble any one part of the standard chromosome complement. There was a preponderance of females among the 19 cases. Chromosome analysis of the parents in the 14 most recent cases revealed maternal chromosome abnormalities in 11 (79%). Of these 11, eight mothers had balanced reciprocal translocations; nondisjunction led to the smaller of their translocation chromosomes being passed on as the supernumerary chromosome in their offspring. Thus, nondisjunction of maternal translocations accounts for a major proportion of the unusual supernumerary chromosomes found by our laboratory. Advanced maternal age was noted in this group of mothers. Three mothers had supernumerary chromosomes themselves. We conclude that unusual supernumerary chromosomes (1) are not rare among patients referred for chromosome studies; (2) are generally not simple products of breakage; (3) are very frequently the result of malsegregation of a balanced maternal reciprocal translocation; and (4) are very difficult to characterize unless a balanced parental translocation is identified. Parental karyotypes should be obtained whenever a patient has an extra, unusual chromosome.     

Mutation and selection in a large population

In this paper we study a large, but finite population, in which mutation and selection occur at a single genetic locus in a diploid organism. We provide theoretical results for the equilibrium allele frequencies, their variances and covariances and their equilibrium distribution, when the population size is larger than the reciprocal of the mean allelic mutation rate. We are also able to infer that the equilibrium distribution of allele frequencies takes the form of a constrained multivariate Gaussian distribution. Our results provide a rapid way of obtaining useful information in the case of complex mutation and selection schemes when the population size is large. We present numerical simulations to test the applicability of our theoretical formulations. The results of these simulations are in very reasonable agreement with the theoretical predictions.     

Ear lobe crease: incidence in a healthy Malay population

The incidence of ear lobe crease (ELC) was studied in 1576 healthy Malay subjects (566 males and 1010 females), randomly selected from the residents of Kota Bharu, Malaysia. ELC was present in 31.1% of males and in 3.6% of females; this difference in incidence between the two sexes is statistically significant (p > 0.05). In males the incidence of Type I crease was highest (10.1%) while that of Type III crease was lowest (2.3%). In females Type II crease showed the highest incidence (1.9%) and Type III the lowest. The incidence of bilateral presence of all three types of ELC showed an age-related increase in males. The ELC often starts unilaterally and later develops bilaterally and earlier in males than in females.     

Natural selection associated with color vision defects in some population groups of Eurasia

Fitness coefficients and other quantitative parameters of selection associated with the generalized color blindness gene CB+ were obtained for three ethnogeographic population groups, including Belarusians from Belarus, ethnic populations of the Volga-Ural region, and ethnic populations of Siberia and the Far East of Russia. All abnormalities encoded by the OPN1LW and OPN1MW loci were treated as deviations from normal color perception. Coefficients were estimated from an approximation of the observed CB+ frequency distributions to the theoretical stationary distribution for the Wright island model. This model takes into account the pressure of migrations, selection, and random genetic drift, while the selection parameters are represented in the form of the distribution parameters. In the populations of Siberia and Far East, directional selection in favor of normal color vision and the corresponding allele CB- was observed. In the Belarusian and ethnic populations of the Volga-Ural region, stabilizing selection was observed. The selection intensity constituted 0.03 in the Belarusian; 0.22 in the ethnic populations of the Volga-Ural region; and 0.24 in ethnic populations of Siberia and Far East.     

Deciduous enamel defects and caries susceptibility in a prehistoric Ohio population

Clinical studies of the relationship between developmental enamel defects and caries susceptibility have often produced conflicting results. This has been due in part to a failure to distinguish between different types of defects. Studies of this association in prehistoric populations have been rare. The complete deciduous dentitions of 57 subadults from the Libben site, a large Late Woodland cemetery in Ottawa County, Ohio, were selected for analysis. Defects were classified as either hypoplasias (deficiencies in matrix apposition) or hypocalcifications (deficiencies in mineralization) and were graded for severity. The presence or absence of carious lesions was recorded for each tooth. Results indicate a strong positive relationship between hypocalcifications and caries susceptibility. The elevated caries susceptibility of hypocalcified teeth may be related to high levels of magnesium or altered enamel microcrystallite orientation within these teeth. Variations in the frequency of hypocalcifications may partially explain differences in caries rates that have been observed in different prehistoric populations.     

Sexual cannibalism: high incidence in a natural population with benefits to females

Background

Sexual cannibalism may be a form of extreme sexual conflict in which females benefit more from feeding on males than mating with them, and males avoid aggressive, cannibalistic females in order to increase net fitness. A thorough understanding of the adaptive significance of sexual cannibalism is hindered by our ignorance of its prevalence in nature. Furthermore, there are serious doubts about the food value of males, probably because most studies that attempt to document benefits of sexual cannibalism to the female have been conducted in the laboratory with non-natural alternative prey. Thus, to understand more fully the ecology and evolution of sexual cannibalism, field experiments are needed to document the prevalence of sexual cannibalism and its benefits to females.

Methodology/Principal Findings

We conducted field experiments with the Mediterranean tarantula (Lycosa tarantula), a burrowing wolf spider, to address these issues. At natural rates of encounter with males, approximately a third of L. tarantula females cannibalized the male. The rate of sexual cannibalism increased with male availability, and females were more likely to kill and consume an approaching male if they had previously mated with another male. We show that females benefit from feeding on a male by breeding earlier, producing 30% more offspring per egg sac, and producing progeny of higher body condition. Offspring of sexually cannibalistic females dispersed earlier and were larger later in the season than spiderlings of non-cannibalistic females.

Conclusions/Significance

In nature a substantial fraction of female L. tarantula kill and consume approaching males instead of mating with them. This behaviour is more likely to occur if the female has mated previously. Cannibalistic females have higher rates of reproduction, and produce higher-quality offspring, than non-cannibalistic females. Our findings further suggest that female L. tarantula are nutrient-limited in nature and that males are high-quality prey. The results of these field experiments support the hypothesis that sexual cannibalism is adaptive to females.     

Cancer incidence in a population living near a petrochemical facility and oil refinery

There is growing concern that pollution from petrochemical and oil refinery installations in Pancevo (Serbia) has increased the incidence of various diseases including cancer. The aim of our study was to investigate cancer incidence in Pancevo and to compare it with the region of central Serbia. Cancer incidence data were obtained from the corresponding Serbian Cancer Registries. Systematic local monitoring of benzene, toluene and methyl mercaptane in the atmosphere within Pancevo's industrial area indicated that the average monthly and yearly concentrations often exceeded permitted levels proposed by EU standards (5 microgm(-3)). Cancer incidence was lower in Pancevo than in central Serbia (the standardised incidence for all types of cancers in Pancevo was 218.3 and in central Serbia it was 241.7 per 100,000 inhabitants). The available data do not allow us to correlate air pollution in Pancevo with increased cancer incidence.     

Genetic polymorphisms of the TYMS gene are not associated with congenital cardiac septal defects in a Han Chinese population

Background

Clinical research indicates that periconceptional administration of folic acid can reduce the occurrence of congenital cardiac septal defects (CCSDs). The vital roles of folate exhibits in three ways: the unique methyl donor for DNA expression regulation, the de novo biosynthesis of purine and pyrimidine for DNA construction, and the serum homocysteine removal. Thymidylate synthase (TYMS) is the solo catalysis enzyme for the de novo synthesis of dTMP, which is the essential precursor of DNA biosynthesis and repair process. To examine the role of TYMS in Congenital Cardiac Septal Defects (CCSDs) risk, we investigated whether genetic polymorphisms in the TYMS gene associated with the CCSDs in a Han Chinese population.

Method

Polymorphisms in the noncoding region of TYMS were identified via direct sequencing in 32 unrelated individuals composed of half CCSDs and half control subjects. Nine SNPs and two insertion/deletion polymorphisms were genotyped from two independent case-control studies involving a total of 529 CCSDs patients and 876 healthy control participants. The associations were examined by both single polymorphism and haplotype tests using logistic regression.

Result

We found that TYMS polymorphisms were not related to the altered CCSDs risk, and even to the changed risk of VSDs subgroup, when tested in both studied groups separately or in combination. In the haplotype analysis, there were no haplotypes significantly associated with risks for CCSDs either.

Conclusion

Our results show no association between common genetic polymorphisms of the regulatory region of the TYMS gene and CCSDs in the Han Chinese population.     

A review of limb defects in a large fetus collection.

Although a considerable number of papers have been published dealing with the frequency and variety of genetic and nongenetic limb defects in newborns and to a lesser extent among embryos, little has been published about the range of limb defects among spontaneously aborted middle and late-term fetuses. This study reports on 133 limb defects from the Central Laboratory for Human Embryology (CLHE), Seattle, Washington. These constitute 34.1% of the total defective specimens in the collection and 5.4% of the total collection population. It is proposed that 30% of the limb defects described indicate a definite recurrence risk, 27% do not indicate recurrence, and the recurrence risk for 43% is unknown. The most interesting findings from this study include the observation that reduction defects affect predominantly the preaxial side of the upper limb and that addition defects (polydactyly) affect predominantly the postaxial side of the lower limb. The observation in relation to reduction defects agrees with U.S. newborn studies. The observation in relation to polydactyly is exactly opposite the studies of Latin American newborns and Japanese embryos.     

Diagnosed hypertension in Canada: incidence, prevalence and associated mortality

Background:

Hypertension is a leading risk factor for cardiovascular diseases. Our objectives were to examine the prevalence and incidence of diagnosed hypertension in Canada and compare mortality among people with and without diagnosed hypertension.

Methods:

We obtained data from linked health administrative databases from each province and territory for adults aged 20 years and older. We used a validated case definition to identify people with hypertension diagnosed between 1998/99 and 2007/08. We excluded pregnant women from the analysis.

Results:

This retrospective population-based study included more than 26 million people. In 2007/08, about 6 million adults (23.0%) were living with diagnosed hypertension and about 418 000 had a new diagnosis. The age-standardized prevalence increased significantly from 12.5% in 1998/99 to 19.6% in 2007/08, and the incidence decreased from 2.7 to 2.4 per 100. Among people aged 60 years and older, the prevalence was higher among women than among men, as was the incidence among people aged 75 years and older. The prevalence and incidence were highest in the Atlantic region. For all age groups, all-cause mortality was higher among adults with diagnosed hypertension than among those without diagnosed hypertension.

Interpretation:

The overall prevalence of diagnosed hypertension in Canada from 1998 to 2008 was high and increasing, whereas the incidence declined during the same period. These findings highlight the need to continue monitoring the effectiveness of efforts for managing hypertension and to enhance public health programs aimed at preventing hypertension.Globally, raised blood pressure is the leading risk factor for death, accounting for about 13% of all deaths,^1,2 and it is the strongest risk factor for lost years of healthy life.¹ Left untreated, hypertension can increase the risk of stroke, coronary artery disease, dementia, heart and kidney failure, and other chronic diseases.^3–6 Managing hypertension through lifestyle modification or the use of antihypertensive medications, or both, can help mitigate these outcomes.⁷ Over the past decades in Canada, mortality associated with cardiovascular diseases has decreased,⁸ partly because of increased awareness and diagnosis of hypertension and better control of blood pressure.^9,10 However, the prevalence of hypertension remains high, and currently there are no mechanisms to track new cases at the national level.To date, information about hypertension in Canada has been mainly obtained by health surveys conducted at the provincial or national levels. Such surveys typically provide prevalence (not incidence) data and include limited data about trends over time.^11–15 National health surveys in Canada are resource intensive, do not include information about people who live in remote areas or institutions, and may underestimate hypertension prevalence because of recall bias and non-response.¹⁶ The use of administrative data that is population-based and routinely collected, such as physician claims and hospital discharge data, allows for a more comprehensive picture of this condition. Other important advantages of using administrative data include the readiness of the data to be analyzed, cost-efficiency, wide geographic coverage and the relatively complete capture of patient contact with the health care system (i.e., less prone to selection bias).Several recent studies in Canada and the United States have established valid methods for using administrative data to identify cases of hypertension.^16–23 In a study conducted in Ontario involving women and men aged 20 years and older, Tu and colleagues found that the prevalence and incidence of diagnosed hypertension were 24.5% in 2005 and 3.2% in 2004, respectively.²⁴ We used the same validated case definition to examine the prevalence and incidence of diagnosed hypertension in Canada from 1998/99 to 2007/08 by age and by province and territory. We also compared all-cause mortality by age and sex among those with and without diagnosed hypertension.     

The prevention and repair of large abdominal-wall defects by muscle transposition: a preliminary communication

Abdominal-wall defects, whether occurring as perioperative or postoperative phenomena, have been variously managed. Where the defect cannot be repaired by the use of the patient's own tissues, synthetic material is commonly utilized. Where both the preceding are unsuccessful, closure by means of muscles transferred from the thigh should be considered. Muscles have distinct advantages over fascial grafts or synthetic materials: they are dynamic structures that are effective in controlling herniae, may relieve symptoms in the case of symptomatic scoliosis resulting from the muscle loss, and may improve bowel action by improving expulsive abdominal efforts. Preliminary experience with for patients is presented, together with details of the operative technique. Since this report was submitted, a fifth patient suffering from a congenital "prune belly" syndrome has been treated.     

Studies on a population of large termite mounds in Uganda

• 1 Two study-sites near Kampala were mapped and all of the termite mounds within them were measured. Changes were recorded in the three succeeding years. A method was developed for estimating mound volumes from height and diameter.
• 2 Macrotermes bellicosus mounds reached a volume of about 2.4 m³ in 3 years after which they grew more slowly to a maximum from 4 to 6 m³. Growth in volume during the first 3 years was approximately linear and its rate did not vary seasonally, probably because growth is related to temperature which was nearly constant throughout the year.
• 3 M.bellicosus mounds had an average length of life of about 10 years, although colonies survived on average only 4 years. The corresponding figures for Pseudacanthotermes spp. were 5 and 2 1/2 years. Some mounds were recolonized after the death of the original colony.
• 5 Fresh earth was brought up at a minimum rate of about 10 m³ ha^-1 yr^-1 but more was lost by erosion and destruction and the populations of mounds were decreasing.
• 4 The number of ventilation shafts in M.bellicosus mounds increased with the volume of the mound. Many mounds, both dead and alive, supported vegetation.
• 6 Local opinion is that Pseudacanthotermes are harmless but M.bellicosus is regarded as a pest and attempts are made to destroy its mounds.

     

Extinction time and age of an allele in a large finite population

For a single locus with two alleles we study the expected extinction and fixation times of the alleles under the influence of selection and genetic drift. Using a diffusion model we derive asymptotic approximations for these expected exit times for large populations. We consider the case where the fitness of the heterozygote is in between the fitnesses of the homozygotes (incomplete dominance). The asymptotic analysis not only yields new quantitative results but also reveals interesting features that remain hidden in the exact solution. Some of the outcomes are extensions of results known in the literature. The asymptotic approximations also apply to the expected first arrival time of an allele at a specified frequency and to the expected age of an allele.     

Identification of bacteria in biofilm and bulk water samples from a nonchlorinated model drinking water distribution system: detection of a large nitrite-oxidizing population associated with Nitrospira spp

In a model drinking water distribution system characterized by a low assimilable organic carbon content (<10 microg/liter) and no disinfection, the bacterial community was identified by a phylogenetic analysis of rRNA genes amplified from directly extracted DNA and colonies formed on R2A plates. Biofilms of defined periods of age (14 days to 3 years) and bulk water samples were investigated. Culturable bacteria were associated with Proteobacteria and Bacteriodetes, whereas independently of cultivation, bacteria from 12 phyla were detected in this system. These included Acidobacteria, Nitrospirae, Planctomycetes, and Verrucomicrobia, some of which have never been identified in drinking water previously. A cluster analysis of the population profiles from the individual samples divided biofilms and bulk water samples into separate clusters (P = 0.027). Bacteria associated with Nitrospira moscoviensis were found in all samples and encompassed 39% of the sequenced clones in the bulk water and 25% of the biofilm community. The close association with Nitrospira suggested that a large part of the population had an autotrophic metabolism using nitrite as an electron donor. To test this hypothesis, nitrite was added to biofilm and bulk water samples, and the utilization was monitored during 15 days. A first-order decrease in nitrite concentration was observed for all samples with a rate corresponding to 0.5 x 10(5) to 2 x 10(5) nitrifying cells/ml in the bulk water and 3 x 10(5) cells/cm(2) on the pipe surface. The finding of an abundant nitrite-oxidizing microbial population suggests that nitrite is an important substrate in this system, potentially as a result of the low assimilable organic carbon concentration. This finding implies that microbial communities in water distribution systems may control against elevated nitrite concentrations but also contain large indigenous populations that are capable of assisting the depletion of disinfection agents like chloramines.