Infrared video thermography: a technique for assessing cold adaptation in insects

Insects can survive subzero temperatures by two main strategies: freeze tolerance and freeze avoidance. An array of techniques have been used to investigate the physiological limits of insects to low temperatures, such as differential scanning calorimetry, temperature-controlled cooling apparatus, thermocouples, and computer-controlled chart recording equipment. However, these techniques require animals to be stationary, precluding behavioral data. We used infrared video thermography to investigate cold adaptation in an alpine insect, expanding such investigations to include behavioral response as an indicator of physiological stress. This technique is noninvasive and provides a large amount of physiological information, such as supercooling points, lower lethal temperatures, and hemolymph melting points. Insect supercooling points in response to a constant cooling rate were variable; however, temperatures at the initiation of behavioral stress response were less variable. Assessments of supercooling points and lower lethal temperatures obtained in this way are more biologically meaningful because allowing unhindered movement of insects more closely resembles natural environments.     

Rhodopsin determinants for transducin activation: a gain-of-function approach

Three cytoplasmic loops in the G protein-coupled receptor rhodopsin, C2, C3, and C4, have been implicated as key sites for binding and activation of the visual G protein transducin. Non-helical portions of the C2- and C3-loops and the cytoplasmic helix-8 from the C4 loop were targeted for a "gain-of-function" mutagenesis to identify rhodopsin residues critical for transducin activation. Mutant opsins with residues 140-148 (C2-loop), 229-244 (C3-loop), or 310-320 (C4-loop) substituted by poly-Ala sequences of equivalent lengths served as templates for mutagenesis. The template mutants with poly-Ala substitutions in the C2- and C3-loops formed the 500-nm absorbing pigments but failed to activate transducin. Reverse substitutions of the Ala residues by rhodopsin residues have been generated in each of the templates. Significant ( approximately 50%) restoration of the rhodopsin/transducin coupling was achieved with re-introduction of residues Cys140/Lys141 and Arg147/Phe148 into the C2 template. The reverse substitutions of the C3-loop residues Thr229/Val230 and Ser240/Thr242/Thr243/Gln244 produced a pigment with a full capacity for transducin activation. The C4 template mutant was unable to bind 11-cis-retinal, and the presence of Asn310/Lys311 was required for correct folding of the protein. Subsequent mutagenesis of the C4-loop revealed the role of Phe313 and Met317. On the background of Asn310/Lys311, the inclusion of Phe313 and Met317 produced a mutant pigment with the potency of transducin activation equal to that of the wild-type rhodopsin. Overall, our data support the role of the three cytoplasmic loops of rhodopsin and suggest that residues adjacent to the transmembrane helices are most important for transducin activation.     

Genetic determinants of Tibetan high-altitude adaptation

Some highland populations have genetic adaptations that enable their successful existence in a hypoxic environment. Tibetans are protected against many of the harmful responses exhibited by non-adapted populations upon exposure to severe hypoxia, including elevated hemoglobin concentration (i.e., polycythemia). Recent studies have highlighted several genes subject to natural selection in native high-altitude Tibetans. Three of these genes, EPAS1, EGLN1 and PPARA, regulate or are regulated by hypoxia inducible factor, a principal controller of erythropoiesis and other organismal functions. Uncovering the molecular basis of hypoxic adaptation should have implications for understanding hematological and other adaptations involved in hypoxia tolerance. Because the hypoxia response involves a variety of cardiovascular, pulmonary and metabolic functions, this knowledge would improve our understanding of disease mechanisms and could ultimately be translated into targeted therapies for oxygen deprivation, cardiopulmonary and cerebral pathologies, and metabolic disorders such as diabetes and obesity.     

Cross-cultural dimensions of breastfeeding practices and abstinence: Evidence from Uttar Pradesh and Tamilnadu, India

Summary and Conclusion The analysis contained in this paper brings out very clearly that the practice of breastfeeding and abstinence in the two major states of India: Uttar Pradesh and Tamilnadu are highly related to socio-cultural factors and changes in generational gaps. The findings reveal that literate, non-Hindu, and rich (high SLI) women have shorter breastfeeding durations than illiterates, Hindus, and poor (low SLI) women of Uttar Pradesh and Tamilnadu. In addition, the breastfeeding practice in Uttar Pradesh is influenced by residence background and generational age-gaps. The role of socio-cultural factors in influencing post-partum sexual abstinence period has been found to be significantly important through the variables; residence background, generational age-gaps, religion and working status of women. The results reveal that urban women, of younger cohorts (below 30 years), non-Hindu, and non-working women have shorter abstinence periods compared to rural women, of older cohorts (above 30 years), Hindus, and working women in both the states. The findings from this analysis suggest that apart from modernization process, defined in terms of higher literacy levels, higher developmental and urbanization levels, the changing perceptions and attitude towards lactational practices over the generation has significant dent on shortening of breastfeeding durations and abstinence periods. Thus, the study support the hypothesis that the process of modernization defined in terms of improvement in level of education, family income, urbanization tends to shorten the period of breastfeeding and abstinence, and consequently, the post-partum infecundability is reduced. Such reductions in the infertile periods can be expected to contribute to an increase in natural fertility levels of the population and also on the observed fertility levels, if not counter balanced by the fertility reducing effects of contraception.     

Ovulation: a multi-gene, multi-step process

The luteinizing hormone (LH) surge initiates a cascade of proteolytic events that control ovulation. One of the genes induced by LH is the progesterone receptor (PR). Because mice with a mutant PR gene (PRKO) fail to ovulate and are infertile, we have used them as a model in which to determine PR target genes that might mediate the ovulatory process. The matrix metalloproteinases (MMPs: MMP2, MMP9, and MMP13) appear to be expressed in ovaries of PRKO mice in a manner similar to that in their wild-type littermates. However, the expression of two other types of proteases, cathepsin L (a member of the papain family) and ADAMTS-1 (A Disintegrin And Metalloproteinase with Thrombospondin-like motifs), are selectively induced in granulosa cells of preovulatory follicles by the LH surge. Maximal levels of these proteases are observed at 12-16 h after an LH surge, the time of ovulation. Furthermore, mRNAs encoding cathepsin L and ADAMTS-1 are reduced in the PRKO mice compared to their wild-type littermates. These novel observations indicate that these two proteases regulate some key step(s) controlling ovulation.     

Structural determinants of cold adaptation and stability in a large protein

The heat-labile alpha-amylase from an antarctic bacterium is the largest known protein that unfolds reversibly according to a two-state transition as shown by differential scanning calorimetry. Mutants of this enzyme were produced, carrying additional weak interactions found in thermostable alpha-amylases. It is shown that single amino acid side chain substitutions can significantly modify the melting point T(m), the calorimetric enthalpy Delta H(cal), the cooperativity and reversibility of unfolding, the thermal inactivation rate constant, and the kinetic parameters k(cat) and K(m). The correlation between thermal inactivation and unfolding reversibility displayed by the mutants also shows that stabilizing interactions increase the frequency of side reactions during refolding, leading to intramolecular mismatches or aggregations typical of large proteins. Although all mutations were located far from the active site, their overall trend is to decrease both k(cat) and K(m) by rigidifying the molecule and to protect mutants against thermal inactivation. The effects of these mutations indicate that the cold-adapted alpha-amylase has lost a large number of weak interactions during evolution to reach the required conformational plasticity for catalysis at low temperatures, thereby producing an enzyme close to the lowest stability allowing maintenance of the native conformation.     

Cross-cultural patterns of marriage and inheritance: A phylogenetic approach

There is a strong correlation between marriage system and wealth inheritance pattern across societies (Hartung 1982); as the degree of polygyny increases, so too does the degree of male bias in inheritance. In this paper, we reevaluate this pattern using a new technique in cross-cultural analyses that effectively controls for the nonindependence of cultures (Galton's problem) through the identification of independent instances of cultural change (Mace and Pagel 1994). First, we produce cultural phylogenetic trees for the societies under study, from phylogenies previously constructed on the basis of linguistic similarity (Ruhlen 1987). Then, following standard methods for the analysis of discrete characters on phylogenetic trees, we use parsimony to determine the ancestral condition of both marriage and inheritance, and subsequently tally the number of independent instances of cultural change in each trait. The results show that transitions to polygyny are much more commonly associated with male-biased inheritance than are transitions to monogamy across human societies in our sample. They illustrate how the degree of change in the evolution of these traits differs considerably between divergent cultural groups. The advantages of this technique are discussed.     

Salt stress adaptation of Bacillus subtilis: a physiological proteomics approach

The adaptation to osmotic stress is crucial for growth and survival of Bacillus subtilis in its natural ecosystem. Dual channel imaging and warping of 2-D protein gels were used to visualize global changes in the protein synthesis pattern of cells in response to osmotic stress (6% NaCl). Many vegetative enzymes were repressed in response to salt stress and derepressed after resumption of growth. The enzymes catalyzing the metabolic steps from glucose to 2-oxoglutarate, however, were almost constantly synthesized during salt stress despite the growth arrest. This indicates an enhanced need for the proline precursor glutamate. The synthesis of enzymes involved in sulfate assimilation and in the formation of Fe-S clusters was also induced, suggesting an enhanced need for the formation or repair of Fe-S clusters in response to salt stress. One of the most obvious changes in the protein synthesis profile can be followed by the very strong induction of the SigB regulon. Furthermore, members of the SigW regulon and of the PerR regulon, indicating oxidative stress after salt challenge, were also induced. This proteomic approach provides an overview of cell adaptation to an osmotic upshift in B. subtilis visualizing the most dramatic changes in the protein synthesis pattern.     

Work related determinants of breastfeeding discontinuation among employed mothers in Malaysia

Background

This cross-sectional study assesses factors that contribute to discontinuing breastfeeding among employed mothers in Malaysia.

Methods

A structured questionnaire was used in conducting this study involving all government health clinics in Petaling district between July and September 2006. Respondents were Malaysian women with children between the ages of six to twelve months who were formally employed. Factors studied were selected socio-demographic and work-related characteristics.

Results

From a total of 290 respondents, 51% discontinued breastfeeding. The majority (54%) of mothers who discontinued breastfeeding had breastfed their babies for less than three months. Compared to Malay mothers, the risk of breastfeeding discontinuation were higher among Chinese (AOR 3.7, 95% CI: 1.7, 7.8) and Indian mothers (AOR 7.3, 95% CI 1.9, 27.4). Not having adequate breastfeeding facilities at the workplace was also a risk factor for breastfeeding discontinuation (AOR 1.8, 95% CI: 1.05, 3.1).

Conclusion

It is important that workplaces provide adequate breastfeeding facilities such as a room in which to express breast milk and a refrigerator, and allow mothers flexible time to express breast milk.     

Protein and DNA sequence determinants of thermophilic adaptation

There have been considerable attempts in the past to relate phenotypic trait—habitat temperature of organisms—to their genotypes, most importantly compositions of their genomes and proteomes. However, despite accumulation of anecdotal evidence, an exact and conclusive relationship between the former and the latter has been elusive. We present an exhaustive study of the relationship between amino acid composition of proteomes, nucleotide composition of DNA, and optimal growth temperature (OGT) of prokaryotes. Based on 204 complete proteomes of archaea and bacteria spanning the temperature range from −10 °C to 110 °C, we performed an exhaustive enumeration of all possible sets of amino acids and found a set of amino acids whose total fraction in a proteome is correlated, to a remarkable extent, with the OGT. The universal set is Ile, Val, Tyr, Trp, Arg, Glu, Leu (IVYWREL), and the correlation coefficient is as high as 0.93. We also found that the G + C content in 204 complete genomes does not exhibit a significant correlation with OGT (R = −0.10). On the other hand, the fraction of A + G in coding DNA is correlated with temperature, to a considerable extent, due to codon patterns of IVYWREL amino acids. Further, we found strong and independent correlation between OGT and the frequency with which pairs of A and G nucleotides appear as nearest neighbors in genome sequences. This adaptation is achieved via codon bias. These findings present a direct link between principles of proteins structure and stability and evolutionary mechanisms of thermophylic adaptation. On the nucleotide level, the analysis provides an example of how nature utilizes codon bias for evolutionary adaptation to extreme conditions. Together these results provide a complete picture of how compositions of proteomes and genomes in prokaryotes adjust to the extreme conditions of the environment.     

Disentangling genetic and epigenetic determinants of ultrafast adaptation

A major rationale for the advocacy of epigenetically mediated adaptive responses is that they facilitate faster adaptation to environmental challenges. This motivated us to develop a theoretical–experimental framework for disclosing the presence of such adaptation‐speeding mechanisms in an experimental evolution setting circumventing the need for pursuing costly mutation–accumulation experiments. To this end, we exposed clonal populations of budding yeast to a whole range of stressors. By growth phenotyping, we found that almost complete adaptation to arsenic emerged after a few mitotic cell divisions without involving any phenotypic plasticity. Causative mutations were identified by deep sequencing of the arsenic‐adapted populations and reconstructed for validation. Mutation effects on growth phenotypes, and the associated mutational target sizes were quantified and embedded in data‐driven individual‐based evolutionary population models. We found that the experimentally observed homogeneity of adaptation speed and heterogeneity of molecular solutions could only be accounted for if the mutation rate had been near estimates of the basal mutation rate. The ultrafast adaptation could be fully explained by extensive positive pleiotropy such that all beneficial mutations dramatically enhanced multiple fitness components in concert. As our approach can be exploited across a range of model organisms exposed to a variety of environmental challenges, it may be used for determining the importance of epigenetic adaptation‐speeding mechanisms in general.     

Visual cycle and dark adaptation: a new approach in research

Visual cycle is the series of reactions that support regeneration of the visual pigmen after its photolysis in retinal rods and cones. Inherited or acquired deficiencies of the visual cycle impair dark adaptation and lead to a series of visual disorders. The paper describes a new approach to study of the visual cycle that uses fast dichroic microspectrophotometer. The method allows studying interconversion of bleaching products in single intact photoreceptors in condition approaching the situation in vivo. Using this approach, we established a complete scheme of transitions between metarhodopsins, retinal and retinol in amphibian rods. It appeared that the decay of metarhodopsins controls both the time course of rod dark adaptation following small bleaches and the production of retinol that is the substrate for rhodopsin regeneration. We also obtained novel data on kinetics of the decay of cone metapigments that was found to be by an order of magnitude faster than in rods. Possible application of the method for further study of the visual cycle in normal and pathological conditions is discussed.     

The dynamics of adaptation: an illuminating example and a Hamilton-Jacobi approach

Our starting point is a selection-mutation equation describing the adaptive dynamics of a quantitative trait under the influence of an ecological feedback loop. Based on the assumption of small (but frequent) mutations we employ asymptotic analysis to derive a Hamilton-Jacobi equation. Well-established and powerful numerical tools for solving the Hamilton-Jacobi equations then allow us to easily compute the evolution of the trait in a monomorphic population when this evolution is continuous but also when the trait exhibits a jump. By adapting the numerical method we can, at the expense of a significantly increased computing time, also capture the branching event in which a monomorphic population turns dimorphic and subsequently follow the evolution of the two traits in the dimorphic population. From the beginning we concentrate on a caricatural yet interesting model for competition for two resources. This provides the perhaps simplest example of branching and has the great advantage that it can be analyzed and understood in detail.     

Import of proteins into mitochondria: a multi-step process

Translocation of precursor proteins from the cytosol into mitochondria is a multi-step process. The generation of translocation intermediates, i.e. the reversible accumulation of precursors at distinct stages of their import pathway into mitochondria ('translocation arrest'), has allowed the experimental characterization of distinct functional steps of protein import. These steps include: ATP-dependent unfolding of precursors; specific recognition of precursors by distinct receptors on the mitochondrial surface; interaction of precursors; specific recognition of precursors by distinct receptors on the mitochondrial surface; interaction of precursors with a general insertion protein ('GIP') in the outer mitochondrial membrane; membrane-potential-dependent translocation into the inner membrane at contact sites between both membranes; proteolytic processing of precursors; and intramitochondrial sorting of precursors via the matrix space ('conservative sorting'). The functional characteristics unveiled by studying mitochondrial protein import appear to be of general interest for investigations on intracellular protein sorting.     

A note on the determinants of breastfeeding durations in an African country

This paper utilizes data from the 1977-78 Kenya Fertility Survey, 1 component of the World Fertility Survey, to analyze the determinants of breastfeeding durations for women 15 to 50 years old who had their last-but-1 live birth between 3 and 15 years prior to the interview. Comparisons are made with the findings fro m the World Fertility Surveys in 8 other developing countries in Asia and Latin America. Findings indicate that literacy, urban residence, secondary school education, and modern employment reduce the duration of breastfeeding in Kenya. In addition, the subgroups of women who appear to be curtailing breastfeeding are growing in proportional size or are composed of women may be innovators or leaders. A continuation of this pattern into the future may increase levels of infant morbidity and mortality and, in the absence of increased modern contraceptive practice, may increase the societal level of fertility. The death of the infant curtails the period of breastfeeding. Although there is a pronounced preference for male children in Kenya, this preference does not lead to differential durations of breastfeeding by sex of child. About 10% of Kenyan women used contraception in the last closed interval. Parity and age explain less than 1% of the variation in duration of breastfeeding in Kenya. Kenyan women are among the least likely to have attended secondary school, to have worked since marriage, and to have used modern contraception. The most traditional groups of Kenyan women, those who are Muslim or who are in polygamous unions, breastfeed for the longest durations. The Kenya Fertility Survey suggests that the subgroup of women with some secondary school education is growing considerably. Kikuyu women may be regarded as innovators in many respects. In addition to having shorter breastfeeding durations, they are the least likely to be in polygamous unions or to want more children, and they are the most likely to be using contraception.     

A note on the determinants of breastfeeding durations in an African country

Abstract

This paper utilizes data from the 1977–78 Kenya Fertility Survey, one component of the World Fertility Survey, to analyze the determinants of breastfeeding durations for women 15 to 50 years old who had their last‐but‐one live birth between 3 and 15 years prior to the interview. Comparisons are made with the findings from the World Fertility Surveys in eight other developing countries in Asia and Latin America. Findings indicate that literacy, urban residence, secondary school education, and modern employment reduce the duration of breastfeeding in Kenya. In addition, the subgroups of women who appear to be curtailing breastfeeding are growing in proportional size or are composed of women who may be innovators or leaders. A continuation of this pattern into the future may increase levels of infant morbidity and mortality and, in the absence of increased modern contraceptive practice, may increase the societal level of fertility.     

Infant feeding practices and determinants of poor breastfeeding behavior in Kinshasa,Democratic Republic of Congo: a descriptive study

Background

Although breastfeeding is almost universally accepted in the Democratic Republic (DR) of Congo, by the age of 2 to 3 months 65% of children are receiving something other than human milk. We sought to describe the infant feeding practices and determinants of suboptimal breastfeeding behaviors in DR Congo.

Methods

Survey questionnaire administered to mothers of infants aged?≤?6 months and healthcare providers who were recruited consecutively at six selected primary health care facilities in Kinshasa, the capital.

Results

All 66 mothers interviewed were breastfeeding. Before initiating breastfeeding, 23 gave their infants something other than their milk, including: sugar water (16) or water (2). During the twenty-four hours prior to interview, 26 (39%) infants were exclusively breastfed (EBF), whereas 18 (27%), 12 (18%), and 10 (15%) received water, tea, formula, or porridge, respectively, in addition to human milk. The main reasons for water supplementation included “heat” and cultural beliefs that water is needed for proper digestion of human milk. The main reason for formula supplementation was the impression that the baby was not getting enough milk; and for porridge supplementation, the belief that the child was old enough to start complementary food. Virtually all mothers reported that breastfeeding was discussed during antenatal clinic visit and half reported receiving help regarding breastfeeding from a health provider either after birth or during well-child clinic visit. Despite a median of at least 14 years of experience in these facilities, healthcare workers surveyed had little to no formal training on how to support breastfeeding and inadequate breastfeeding-related knowledge and skills. The facilities lacked any written policy about breastfeeding.

Conclusion

Addressing cultural beliefs, training healthcare providers adequately on breastfeeding support skills, and providing structured breastfeeding support after maternity discharge is needed to promote EBF in the DR Congo.