A general method for constructing increment-decrement life tables that agree with the data

A general method for making increment-decrement life tables is presented. The method involves the finding of probabilities of transition between states, graduated to small intervals of time and age, that are consistent with (i.e., can reproduce) the data, whether the data consist of central age-state specific rates, or some other feature, such as state distributions of a real cohort. The method is then illustrated with a fetal loss life table.     

MODELING AGE-SPECIFIC MORTALITY FOR MARINE MAMMAL POPULATIONS

A method is presented for estimating age-specific mortality based on minimal information: a model life table and an estimate of longevity. This approach uses expected patterns of mammalian survivorship to define a general model of age-specific mortality rates. One such model life table is based on data for northern fur seals (Callorhinus ursinus) using Siler's (1979) 5-parameter competing risk model. Alternative model life tables are based on historical data for human females and on a published model for Old World monkeys. Survival rates for a marine mammal species are then calculated by scaling these models by the longevity of that species. By using a realistic model (instead of assuming constant mortality), one can see more easily the real biological limits to population growth. The mortality estimation procedure is illustrated with examples of spotted dolphins (Stenella attenuata) and harbor porpoise (Phocoena phocoena).     

An integrated database for the enhanced identification of silkworm gene resources

The National Academy of Agricultural Science (NAAS) has developed a web-based database to provide characterization information in silkworm. The silkworm database has four major function menus: variety searching, characterization viewing, general information and photo gallery. It provides 321 silkworm varieties characterization information for six different regions namely, Korean, Japanese, Chinese, European, Tropical and non-classified group. Additionally, the database provides 1,132 photo images regarding life cycle of various silkworm varieties. A specific characterization information table provides accession number, variety, strain and larval marking, blood color, cocoon color, cocoon shape, egg colors, remarks and image table provides photos which consist of shape and color in the different stages of larval, egg and cocoon stages. AVAILABILITY: The database is available for free at http://www.naas.go.kr/silkworm/english/     

Mathematical hazard models of mortality: an alternative to model life tables

A five-parameter competing hazard model of the age pattern of mortality is described, and methods of fitting it to survivorship, death rate, and age structure data are developed and presented. The methods are then applied to published life table and census data to construct life tables for a Late Woodland population, a Christian period Nubian population, and the Yanomama. The advantage of this approach over the use of model life tables is that the hazard model facilitates life-table construction without imposing a particular age pattern of mortality on the data. This development makes it possible to use anthropological data to extend the study of human variation in mortality patterns to small populations.     

Comparative Studies on the Developmental Stages of Three Species of Tropisternus (Coleoptera: Hydrophilidae)

The egg cases, eggs, and different stages of life cycles of Tropisternus lateralis (Fabricius), T. blatchleyi D'Orchymont, and T. collaris (Fabricius) are described. A table is given for separating the various developmental stages of the three species.     

自我重复取样技术与多项式定理在年龄-龄期两性生命表研究中的应用

年龄-龄期两性生命表(age-stage, two-sex life table)简称两性生命表,是种群生态学研究与害虫治理中常用的重要理论与分析工具。根据两性生命表理论而设计的方便用户的软件TWOSEX-MSChart近年来被越来越多国内外学者用于昆虫种群研究的数据分析。两性生命表软件的分析功能是由许多的统计技术与计算机模拟方法作为数据分析的支撑,其中自我重复取样(bootstrap)是其重要技术之一。本文详述了bootstrap技术的基本原理、方法、优缺点及其在两性生命表分析中的应用,并介绍了其理论基础多项式定理(multinomial theorem)在生命表研究中的应用。与常用统计方法相比,bootstrap不需要数据分布假设就可以对数据总体的分布特性进行统计和推断。在两性生命表分析中,bootstrap不仅可以估算种群参数或一般统计值的方差和标准误,同时利用paired bootstrap test还可以比较不同处理间的差异,准确显示种群的变异性。利用相同的自我重复取样样本(same bootstrap samples)可以正确计算昆虫的孵化率与不同繁殖型对种群参数的贡献,并...     

常见寿命数据类型及生命表的编制方法

生命表是描述种群死亡过程的有用工具,介绍了4种常见的寿命数据类型;寿终数据,右删失数据,左删失数据和区间型数据特征及其相应的数据分析处理方法即生命表法,乘积限估计和Turbull估计法,对生命表法和乘积限估计法应用上的特点进行了比较,同时还对特殊的寿命数据类型－－截断数据做了简要介绍。     

Some novel approaches for radioprotection and the beneficial effect of natural products

Due to the increased use of ionizing radiation in various aspects of human life especially in areas pertaining to radiotherapy of cancer, food preservation, agriculture, industry and power generation, there is a need to develop an effective and non-toxic radioprotector. The currently available ones have many drawbacks including high cost, side effects and toxicity. Several novel approaches are on to locate a potent radioprotector. These include mimics of antioxidant enzymes, nitroxides, melatonin, growth factors, gene therapy, hyperthermia apart from natural products. The latter has several advantages since they are non-toxic with proven therapeutic benefits. These can be classified as natural compounds and plant extracts; polyherbal formulations; besides natural and semi-natural compounds of plant origin. A review of the above agents, their efficacy in radioprotection and possible mechanisms responsible has been carried out. As India and many Eastern countries have an enormous heritage of vast natural dietary and time tested medicinal resources it is worth exploring the possibility of developing efficient, economically viable and clinically acceptable radioprotectors for human application from these resources.     

Standards for systems biology

High-throughput technologies are generating large amounts of complex data that have to be stored in databases, communicated to various data analysis tools and interpreted by scientists. Data representation and communication standards are needed to implement these steps efficiently. Here we give a classification of various standards related to systems biology and discuss various aspects of standardization in life sciences in general. Why are some standards more successful than others, what are the prerequisites for a standard to succeed and what are the possible pitfalls?     

Nitric Oxide Cycle in Mammals and the Cyclicity Principle

This paper continues a series of reports considering nitric oxide (NO) and its cyclic conversions in mammals. Numerous facts are summarized with the goal of developing a general concept that would allow the statement of the multiple effects of NO on various systems of living organisms in the form of a short and comprehensive law. The current state of biological aspects of NO research is analyzed in term of elucidation of possible role of these studies in the system of biological sciences. The general concept is based on a notion on cyclic conversions of NO and its metabolites. NO cycles in living organisms and nitrogen turnover in the biosphere and also the Bethe nitrogen–carbon cycle in star matter are considered. A hypothesis that the cyclic organization of processes in living organisms and the biosphere reflects the evolution of life is proposed: the development of physiological functions and metabolism are suggested to be closely related to space and evolution of the Earth as a planet of the Solar System.     

A population model based on a life table that includes marriage and parity.

This paper presents a method for constructing a one-sex life table that incorporates age, marriage and parity. The life table is the basis for a generalized population model, with immediate extension to a stable population differentiated by age, marriage and parity status. The method is quite general and could be extended, without major modification, to more complex life tables.Computation of intrinsic rates of increase for a number of populations adjusted for age, for age and parity, for age and marriage, and for age, marriage and parity shows that adjustment for marriage accounts for most of the difference between the age-adjusted rate and the age-, marriage-, and parity-adjusted rate. Adjustment for parity without adjustment for marriage may be misleading.     

Trachylina: The Group That Remains Enigmatic Despite 150 Years of Investigations

Trachylina is a group of cnidarians, a subclass of Hydrozoa. Despite the low species diversity of this group, its representatives are characterized by diversity of life cycles. Trachylina have populated various environments, from deep ocean to fresh water ecosystems. Polyps of Trachylina are either very small or absent in the life cycle, which distinguishes this group from the majority of other Hydrozoa. Trachylina are also highly diverse and have a number of features that are unusual for cnidarians. A number of representatives of this group are characterized by a small number of cells at the embryonic and larval stages. This phenomenon is well known for the representatives of phylogenetically distant taxa—Nematoda and Chordata (Tunicata). In addition, the development of Trachylina is characterized by a number of evolutionary changes that, apparently, make it possible to accelerate the formation of the definitive stage (medusa). Paradoxically, there is no one species among the representatives of this group that is studied in more or less detail. The purpose of our review is to summarize the scanty information on the Trachylina ontogeny and to demonstrate the importance of studying the ontogeny of this group for understanding the general rules of the evolution of development and life cycles of Metazoa.     

A Test of Equality of Survival Distributions for Two Sample Censored Grouped Survival Data

A common testing problem for a life table or survival data is to test the equality of two survival distributions when the data is both grouped and censored. Several tests have been proposed in the literature which require various assumptions about the censoring distributions. It is shown that if these conditions are relaxed then the tests may no longer have the stated properties. The maximum likelihood test of equality when no assumptions are made about the censoring marginal distributions is derived. The properties of the test are found and it is compared to the existing tests. The fact that no assumptions are required about the censoring distributions make the test a useful initial testing procedure.     

Contingency Table Browser ? prediction of early stage protein structure

The Early Stage (ES) intermediate represents the starting structure in protein folding simulations based on the Fuzzy Oil Drop (FOD) model. The accuracy of FOD predictions is greatly dependent on the accuracy of the chosen intermediate. A suitable intermediate can be constructed using the sequence-structure relationship information contained in the so-called contingency table − this table expresses the likelihood of encountering various structural motifs for each tetrapeptide fragment in the amino acid sequence. The limited accuracy with which such structures could previously be predicted provided the motivation for a more indepth study of the contingency table itself. The Contingency Table Browser is a tool which can visualize, search and analyze the table. Our work presents possible applications of Contingency Table Browser, among them − analysis of specific protein sequences from the point of view of their structural ambiguity.     

Some natural viability systems for a multiallelic locus: a theoretical study

The maintenance of genetic polymorphism under various natural structured viability regimes vs. general unrestricted fitness assignments are compared. The selection models considered include a generalized dominance fitness system, a generalized viability model based on allelic activity values, viability matrices based on multilocus activity levels, viability matrices defined by partitioned "resource" or "substrate" variables, and circulant-type viability matrices. A number of examples that support these formulations are discussed. Detailed results on the nature of the genotype frequency equilibrium configurations for the specified viability models are presented. An increased likelihood for a globally stable equilibrium is predicted for the more structured viability models.     

The multiple decrement life table: a unifying framework for cause-of-death analysis in ecology

Summary The multiple decrement life table is used widely in the human actuarial literature and provides statistical expressions for mortality in three different forms: i) the life table from all causes-of-death combined; ii) the life table disaggregated into selected cause-of-death categories; and iii) the life table with particular causes and combinations of causes eliminated. The purpose of this paper is to introduce the multiple decrement life table to the ecological literature by applying the methods to published death-by-cause information on Rhagoletis pomonella. Interrelations between the current approach and conventional tools used in basic and applied ecology are discussed including the conventional life table, Key Factor Analysis and Abbott's Correction used in toxicological bioassay.     

Evolution in heterogeneous environments: between soft and hard selection

Since their first formulations about half a century ago, the soft and hard selection models have become classical frameworks to study selection in subdivided populations. These models differ in the timing of density regulation and represent two extreme types of selection: density- and frequency-dependent selection (soft) and density- and frequency-independent selection (hard). Yet only few attempts have been made so far to model intermediate scenarios. Here, we design a model where migration may happen twice during the life cycle: before density regulation with probability d(J) (juvenile migration) and after density regulation with probability d(A) (adult migration). In the first step, we analyze the conditions for the coexistence of two specialists. We find that coexistence is possible under a large range of selection types, even when environmental heterogeneity is low. Then, we investigate the different possible outcomes obtained through gradual evolution. We show that polymorphism is more likely to evolve when the trade-off is weak, environmental heterogeneity is high, migration is low, and in particular when juvenile migration is low relative to adult migration, because the timing of migration affects the magnitude of frequency-dependent selection relative to gene flow. This model may provide a more general theoretical framework to experimentally study evolution in heterogeneous environments.     

A general measure of human population growth regulation

A general measure relating the relative effects of mortality and fertility in damping population growth has been derived from stable population theory. This measure, called the Index of Growth Regulation, can be calculated from a life table and a fertility schedule. It is a single number which integrates the fertility and mortality aspects of a population. It has intuitive meaning, and can be related to social aspects of the population. It can be used to compare any two populations, and for this purpose it has advantages over traditional comparative statistics such as life expectancy, which consider only mortality. By selecting life tables representing general stages of human cultural evolution, it has been shown that hunting-gathering populations were regulated more by mortality than by fertility factors. That is, more growth which could have occurred did not occur due to the incidence of mortality than to the incidence of infecundity. The two forces were of about equal weight before the industrial revolution, and fertility has had a predominant role in population regulation since the beginning of industrialization.     

Reconstructed epidermis and full-thickness skin for absorption testing: influence of the vehicles used on steroid permeation

A protocol for percutaneous absorption studies has been validated, based on the use of reconstructed human epidermis (RHE) and aqueous solutions of test substances. However, it is often the case that it is more-complex formulations of drugs or chemicals which will make contact with the skin surface. To investigate whether RHE and the reconstructed full-thickness skin model (FT-model) can be used to predict uptake from formulations, we compared the permeation of hydrocortisone and testosterone when applied in emulsion form and as a solution containing the penetration enhancer, ethanol. Human and pig skin and a non-cornified alveolar model served as references. The results were compared with steroid release from the formulations. The permeation rates of the steroids were ranked as: alveolar model > RHE > FT-model, pig skin > human skin. In accordance with the rapid hydrocortisone release from the formulations, the permeation rates of this steroid exceeded those of testosterone. Only minor differences were observed when comparing the testosterone formulations, in terms of release and permeation. However, the ranking of the permeation of the hydrocortisone formulations was: solution > w/o emulsion > o/w emulsion, which permitted the elucidation of penetration enhancing effects, which is not possible with drug release studies. Differences in penetration were most obvious with native skin and reconstructed tissues, which exhibited a well-developed penetration barrier. In conclusion, RHE and skin preparations may be useful in the development of topical dermatics, and in the framework of hazard analysis of toxic compounds and their various formulations.